General-Purpose, −55°C to +125°C, Wide Bandwidth, DC-Coupled VGA AD8336 Data Sheet FEATURES GENERAL DESCRIPTION Low noise Voltage noise: 3 nV/√Hz Current noise: 3 pA/√Hz Small-signal BW: 115 MHz Large-signal BW: 2 V p-p = 80 MHz Slew rate: 550 V/µs, 2 V p-p Gain ranges (specified) −14 dB to +46 dB 0 dB to 60 dB Gain scaling: 50 dB/V DC-coupled Single-ended input and output Supplies: ±3 V to ±12 V Temperature range: −55°C to +125°C Power 150 mW at ±3 V, −55°C < T < +125°C 84 mW at ±3 V, PWRA = 3 V The AD8336 is a low noise, single-ended, linear in dB, generalpurpose variable gain amplifier, usable over a large range of supply voltages. It features an uncommitted preamplifier with a usable gain range of 6 dB to 26 dB. The VGA gain range is 0 dB to 60 dB, with absolute gain limits of −26 dB to +34 dB. When the preamplifier gain is adjusted for 12 dB, the combined 3 dB bandwidth of the preamplifier and VGA is 100 MHz, and the amplifier is fully usable to 80 MHz. With ±5 V supplies, the maximum output swing is 7 V p-p. Because of the X-AMP® architecture, frequency response is maintained across the entire gain range of the VGA. The differential gain control interface provides precise linear in dB gain scaling of 50 dB/V over the temperature span of −55°C to +125°C and is simple to interface with a variety of external sources. The large supply voltage range makes the AD8336 suited for industrial medical applications and video circuits. Dual-supply operation enables bipolar input signals, such as those generated by photodiodes or photomultiplier tubes. APPLICATIONS Industrial process controls High performance AGC systems I/Q signal processing Video Industrial and medical ultrasound Radar receivers The fully independent voltage feedback preamplifier allows both inverting and noninverting gain topologies. The AD8336 can be used within the specified gain range of −14 dB to +60 dB by selecting a preamplifier gain between 6 dB and 26 dB and choosing appropriate feedback resistors. For the nominal preamplifier gain of 4×, the overall gain range is −14 dB to +46 dB. If required, quiescent power is limited to a safe level by asserting the PWRA pin. FUNCTIONAL BLOCK DIAGRAM AD8336 INPN 5 + PREAMP – PRAO VGAI 8 9 ATTENUATOR –60dB TO 0dB 1 VOUT GAIN CONTROL INTERFACE BIAS PWRA 2 34dB 10 13 3 11 12 VNEG VPOS VCOM GPOS GNEG 06228-001 INPP 4 Figure 1. Rev. D Document Feedback Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 ©2006–2016 Analog Devices, Inc. All rights reserved. Technical Support www.analog.com AD8336 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Setting the Gain .......................................................................... 21 Applications ....................................................................................... 1 Noise ............................................................................................ 21 General Description ......................................................................... 1 Offset Voltage.............................................................................. 21 Functional Block Diagram .............................................................. 1 Applications Information .............................................................. 22 Revision History ............................................................................... 2 Amplifier Configuration ........................................................... 22 Specifications..................................................................................... 3 Preamplifier ................................................................................. 22 Absolute Maximum Ratings ............................................................ 5 Using the Power Adjust Feature ............................................... 23 ESD Caution .................................................................................. 5 Driving Capacitive Loads .......................................................... 23 Pin Configuration and Function Descriptions ............................. 6 Evaluation Board ............................................................................ 24 Typical Performance Characteristics ............................................. 7 Optional Circuitry...................................................................... 24 Test Circuits ..................................................................................... 16 Board Layout Considerations ................................................... 24 Theory of Operation ...................................................................... 20 Outline Dimensions ....................................................................... 27 Overview...................................................................................... 20 Ordering Guide .......................................................................... 27 Preamplifier ................................................................................. 20 VGA.............................................................................................. 20 REVISION HISTORY 5/2016—Rev. C to Rev. D Changes to General Description Section and Figure 1 ............... 1 Changes to Figure 2 and Table 3 ..................................................... 6 Change to Overview Section ......................................................... 20 Updated Outline Dimensions ....................................................... 26 Changes to Ordering Guide .......................................................... 26 5/2011—Rev. B to Rev. C Change to Figure 2 and Table 3 ...................................................... 6 Changes to OG ................................................................................ 26 4/2011—Rev. A to Rev. B Change to Table 2 ............................................................................. 5 Changes to Figure 77 and Preamplifier Section ......................... 20 Changes to Evaluation Board Section, Optional Circuitry Section, and Board Layout Considerations Section ................... 24 Added Table 6.................................................................................. 24 Deleted Figure 83; Renumbered Figures Sequentially ............... 24 Changes to Figure 82, Figure 83, and Figure 84 ......................... 24 Changes to Figure 85, Figure 86, Figure 87, and Figure 88 ....... 25 Deleted Table 6 ................................................................................ 26 9/2008—Rev. 0 to Rev. A Change to General Description Section .........................................1 Deleted Input Capacitance Parameter, Table 1 ..............................3 Added Exposed Pad Notation to Figure 2......................................6 Changes to Figure 11.........................................................................8 Changes to Figure 55...................................................................... 15 Change to Preamplifier Section .................................................... 20 Changes to Noise Section .............................................................. 21 Change to Circuit Configuration for Noninverting Gain Section .................................................................................... 22 Changes to Table 5.......................................................................... 22 Changes to Figure 89 and Table 6................................................. 26 Updated Outline Dimensions ....................................................... 27 Changes to Ordering Guide .......................................................... 27 10/2006—Revision 0: Initial Version Rev. D | Page 2 of 28 Data Sheet AD8336 SPECIFICATIONS VS = ±5 V, T = 25°C, gain range = −14 dB to +46 dB, preamplifier gain = 4×, f = 1 MHz, CL = 5 pF, RL = 500 Ω, PWRA = GND, unless otherwise specified. Table 1. Parameter PREAMPLIFIER −3 dB Small-Signal Bandwidth −3 dB Large-Signal Bandwidth Bias Current, Either Input Differential Offset Voltage Input Resistance Input Capacitance PREAMPLIFIER + VGA −3 dB Small-Signal Bandwidth −3 dB Large-Signal Bandwidth Slew Rate Short-Circuit Preamplifier Input Voltage Noise Spectral Density Input Current Noise Spectral Density Output-Referred Noise DYNAMIC PERFORMANCE Harmonic Distortion HD2 HD3 HD2 HD3 Input 1 dB Compression Point Two-Tone Intermodulation Distortion (IMD3) Output Third-Order Intercept Overdrive Recovery Group Delay Variation Preamplifier Gain = 20× Test Conditions/Comments Min Typ Max Unit 1 VOUT = 10 mV p-p VOUT = 2 V p-p 150 85 725 ±600 900 3 MHz MHz nA μV kΩ pF VOUT = 10 mV p-p VOUT = 10 mV p-p, PWRA = 5 V VOUT = 10 mV p-p, preamplifier gain = 20× VOUT = 10 mV p-p, preamplifier gain = −3× 115 40 20 125 MHz MHz MHz MHz VOUT = 2 V p-p VOUT = 2 V p-p, PWRA = 5 V VOUT = 2 V p-p, preamplifier gain = 20× VOUT = 2 V p-p, preamplifier gain = −3× VOUT = 2 V p-p ±3 V ≤ VS ≤ ±12 V 80 30 20 100 550 3.0 MHz MHz MHz MHz V/µs nV/√Hz VGAIN = 0.7 V, preamplifier gain = 4× VGAIN = −0.7 V, preamplifier gain = 4× VGAIN = 0.7 V, preamplifier gain = 20× VGAIN = −0.7 V, preamplifier gain = 20× VGAIN = 0.7 V, −55°C ≤ T ≤ +125°C VGAIN = −0.7 V, −55°C ≤ T ≤ +125°C 3.0 600 190 2500 200 700 250 pA/√Hz nV/√Hz nV/√Hz nV/√Hz nV/√Hz nV/√Hz nV/√Hz VGAIN = 0 V, VOUT = 1 V p-p f = 1 MHz f = 1 MHz f = 10 MHz f = 10 MHz VGAIN = −0.7 V VGAIN = +0.7 V VGAIN = 0 V, VOUT = 1 V p-p, f1 = 0.95 MHz, f2 = 1.05 MHz VGAIN = 0 V, VOUT = 1 V p-p, f1 = 9.95 MHz, f2 = 10.05 MHz VGAIN = 0 V, VOUT = 2 V p-p, f1 = 0.95 MHz, f2 = 1.05 MHz VGAIN = 0 V, VOUT = 2 V p-p, f1 = 9.95 MHz, f2 = 10.05 MHz VGAIN = 0 V, VOUT = 1 V p-p, f = 1 MHz VGAIN = 0 V, VOUT = 1 V p-p, f = 10 MHz VGAIN = 0 V, VOUT = 2 V p-p, f = 1 MHz VGAIN = 0 V, VOUT = 2 V p-p, f = 10 MHz VGAIN = 0.7 V, VIN = 100 mV p-p to 5 mV p-p 1 MHz < f < 10 MHz, full gain range 1 MHz < f < 10 MHz, full gain range −58 −68 −60 −60 11 −23 −71 −69 −60 −58 34 32 34 33 50 ±1 ±3 dBc dBc dBc dBc dBm dBm dBc dBc dBc dBc dBm dBm dBm dBm ns ns ns Rev. D | Page 3 of 28 AD8336 Parameter ABSOLUTE GAIN ERROR 2 GAIN CONTROL INTERFACE Gain Scaling Factor Intercept Gain Range Input Voltage (VGAIN) Range Input Current Response Time OUTPUT PERFORMANCE Output Impedance, DC to 10 MHz Output Signal Swing Output Current Short-Circuit Current Output Offset Voltage PWRA PIN Normal Power (Logic Low) Low Power (Logic High) Normal Power (Logic Low) Low Power (Logic High) Normal Power (Logic Low) Low Power (Logic High) POWER SUPPLY Supply Voltage Operating Range Quiescent Current VS = ±3 V Data Sheet Test Conditions/Comments −0.7 V < VGAIN < −0.6 V −0.6 V < VGAIN < −0.5 V −0.5 V < VGAIN < +0.5 V −0.5 V < VGAIN < +0.5 V, ±3 V ≤ VS ≤ ±12 V −0.5 V < VGAIN < +0.5 V, −55°C ≤ T ≤ +125°C −0.5 V < VGAIN < +0.5 V, preamplifier gain = −3× 0.5 V < VGAIN < +0.6 V 0.6 V < VGAIN < +0.7 V 48 ±3 V ≤ VS ≤ ±12 V RL ≥ 500 Ω (for |VS| ≤ ±5 V); RL ≥ 1 kΩ above that RL ≥ 1 kΩ (for |VS| = ±12 V) Linear operation − minimum discernable distortion VS = ±3 V VS = ±5 V VS = ±12 V VGAIN = 0.7 V, gain = 200× ±3 V ≤ VS ≤ ±12 V −55°C ≤ T ≤ +125°C 2.5 |VS| − 1.5 |VS| − 2.25 20 +123/−72 +123/−72 +72/−73 −125 −200 −200 Ω V V mA mA mA mA mV mV mV VS = ±3 V VS = ±3 V VS = ±5 V VS = ±5 V VS = ±12 V VS = ±12 V 52 62 +VS +150 0.7 1.5 1.2 2.0 3.2 4.0 ±3 22 VS = ±12 V 2 0 0 Unit 1 dB dB dB dB dB dB dB dB 1 300 −250 49.9 16.4 4.5 60 Max 6 3 +1.25 +1.25 60 dB gain change 58 −VS No foldover −55°C ≤ T ≤ +125°C PWRA = 5 V 1 Typ 1 to 5 0.5 to 1.5 ±0.2 ±0.5 ±0.5 ±0.5 −1.5 to −3.0 −1 to −5 dB/V dB dB dB V μA ns VS = ±5 V Power Supply Rejection Ratio (PSRR) −4.0 −9.0 Preamplifier + VGA VGA only −55°C ≤ T ≤ +125°C PWRA = 3 V Power Dissipation Min 0 0 −1.25 −55°C ≤ T ≤ +125°C PWRA = 5 V VS = ±3 V VS = ±5 V VS = ±12 V VGAIN = 0.7 V, f = 1 MHz All dBm values are calculated with 50 Ω reference, unless otherwise noted. Conformance to theoretical gain expression (see the Setting the Gain section). Rev. D | Page 4 of 28 10 22 10 23 ±12 25 23 to 31 14 26 23 to 31 14 28 24 to 33 16 150 260 672 −40 V V V V V V V 30 mA 18 30 mA 18 31 mA mW mW mW dB Data Sheet AD8336 ABSOLUTE MAXIMUM RATINGS Table 2. Parameter Supply Voltage (VPOS, VNEG) Input Voltage (INPP, INPN) Gain Voltage (GPOS, GNEG) PWRA VGAI Power Dissipation VS ≤ ±5 V ±5 V < VS ≤ ±12 V Operating Temperature Range ±3 V < VS ≤ ±10 V ±10 V < VS ≤ ±12 V Storage Temperature Range Lead Temperature (Soldering 60 sec) Thermal Data 1 θJA θJB θJC ΨJT ΨJB 1 Rating ±15 V VPOS, VNEG VPOS, VNEG 5 V, GND VPOS + 0.6 V, VNEG − 0.6 V Stresses at or above those listed under Absolute Maximum Ratings may cause permanent damage to the product. This is a stress rating only; functional operation of the product at these or any other conditions above those indicated in the operational section of this specification is not implied. Operation beyond the maximum operating conditions for extended periods may affect product reliability. ESD CAUTION 0.43 W 1.12 W −55°C to +125°C −55°C to +85°C −65°C to +150°C 300°C 58.2°C/W 35.9°C/W 9.2°C/W 1.1°C/W 34.5°C/W 4-layer JEDEC board, no airflow, exposed pad soldered to printed circuit board. Rev. D | Page 5 of 28 AD8336 Data Sheet 13 VPOS 14 NC 16 NC 15 NC PIN CONFIGURATION AND FUNCTION DESCRIPTIONS VOUT 1 12 GNEG PWRA 2 AD8336 11 GPOS VCOM 3 TOP VIEW (Not to Scale) 10 VNEG NOTES 1. NC = NO CONNECT. 2. THE EXPOSED PAD IS NOT CONNECTED INTERNALLY. FOR INCREASED RELIABILITY OF THE SOLDER JOINTS AND MAXIMUM THERMAL CAPABILITY, IT IS RECOMMENDED THAT THE PADDLE BE SOLDERED TO THE GROUND PLANE. 06228-002 NC 7 VGAI PRAO 8 NC 6 9 INPN 5 INPP 4 Figure 2. Pin Configuration Table 3. Pin Function Descriptions Pin No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Not applicable Mnemonic VOUT PWRA VCOM INPP INPN NC NC PRAO VGAI VNEG GPOS GNEG VPOS NC NC NC EPAD Description Output Voltage. Power Control. Normal power when grounded; power reduced by half if PWRA is pulled high. Common-Mode Voltage. Normally GND when using a dual supply. Positive Input to Preamplifier. Negative Input to Preamplifier. No Connect. No Connect. Preamplifier Output. VGA Input. Negative Supply. Positive Gain Control Input. Negative Gain Control Input. Positive Supply. No Connect. No Connect. No Connect. The Exposed Pad is Not Connected Internally. For increased reliability of the solder joints and maximum thermal capability, it is recommended that the paddle be soldered to the ground plane. Rev. D | Page 6 of 28 Data Sheet AD8336 TYPICAL PERFORMANCE CHARACTERISTICS VS = ±5 V, T = 25°C, gain range = −14 dB to +46 dB, preamplifier gain = 4×, f = 1 MHz, CL = 5 pF, RL = 500 Ω, PWRA = GND, unless otherwise specified. 2.0 50 T = +125°C T = +25°C T = –55°C 40 1.0 GAIN ERROR (dB) 20 10 0 0.5 0 –0.5 –1.0 –10 –1.5 –600 –400 –200 0 200 VGAIN (mV) 400 600 800 –2.0 –800 06228-003 –20 –800 Figure 3. Gain vs. VGAIN for Three Values of Temperature (T) (See Figure 56) –600 –400 –200 0 200 VGAIN (mV) 400 800 Figure 6. Gain Error vs. VGAIN for Three Values of Temperature (T) (See Figure 56) 50 2.0 VS = ±12V VS = ±5V VS = ±3V 40 600 06228-006 GAIN (dB) 30 VS = ±12V VS = ±5V VS = ±3V 1.5 1.0 GAIN ERROR (dB) 30 GAIN (dB) T = +125°C T = +25°C T = –55°C 1.5 20 10 0.5 0 –0.5 0 –1.0 –10 –600 –400 –200 0 200 VGAIN (mV) 400 600 800 –2.0 –800 06228-004 –20 –800 Figure 4. Gain vs. VGAIN for Three Values of Supply Voltage (VS) (See Figure 56) –400 –200 0 200 VGAIN (mV) 400 600 800 Figure 7. Gain Error vs. VGAIN for Three Values of Supply Voltage (VS) (See Figure 56) 70 2.0 60 1.5 50 PREAMP GAIN = 20× PREAMP GAIN = 4× 1.0 30 PREAMP GAIN = 20× PREAMP GAIN = 4× 20 10 0.5 0 –0.5 0 –1.0 –10 –1.5 –600 –400 –200 200 0 VGAIN (mV) 400 600 800 –2.0 –800 06228-005 –20 –800 Figure 5. Gain vs. VGAIN for Preamplifier Gains of 4× and 20× (See Figure 56) –600 –400 –200 0 200 VGAIN (mV) 400 600 800 Figure 8. Gain Error vs. VGAIN for Preamplifier Gains of 4× and 20× (See Figure 56) Rev. D | Page 7 of 28 06228-008 GAIN ERROR (dB) 40 GAIN (dB) –600 06228-007 –1.5 AD8336 Data Sheet 2.0 50 PREAMP GAIN = PREAMP GAIN = PREAMP GAIN = PREAMP GAIN = 1.5 60 UNITS VGAIN = –0.3V VGAIN = +0.3V 4×, f = 1MHz 4×, f = 10MHz 20×, f = 1MHz 20×, f = 10MHz 40 0.5 % OF UNITS GAIN ERROR (dB) 1.0 0 –0.5 30 20 –1.0 10 Figure 12. Gain Error Histogram 50 PREAMP GAIN = –3×, f = 1MHz PREAMP GAIN = –3×, f = 10MHz PREAMP GAIN = –19×, f = 1MHz PREAMP GAIN = –19×, f = 10MHz 1.5 06228-012 GAIN ERROR (dB) Figure 9. Gain Error vs. VGAIN at 1 MHz and 10 MHz and for Preamplifier Gains of 4× and 20× (See Figure 56) 2.0 0.16 0 0.12 800 0.08 600 0.04 400 –0.04 200 0 VGAIN (mV) –0.08 –200 –0.12 –400 –600 06228-009 –2.0 –800 0 –1.5 60 UNITS –0.3V ≤ VGAIN ≤ 0.3V 40 % OF UNITS 0.5 0 –0.5 30 20 –1.0 10 –1.5 –400 –200 400 200 0 VGAIN (mV) 600 800 0 49.6 49.7 49.8 49.9 50.0 50.1 06228-013 –600 06228-010 –2.0 –800 50.2 GAIN SCALING (dB/V) Figure 10. Gain Error vs. VGAIN at 1 MHz and 10 MHz and for Inverting Preamplifier Gains of −3× and −19× (See Figure 56) Figure 13. Gain Scaling Factor Histogram 50 20 0 40 OUTPUT OFFSET VOLTAGE (mV) VS = ±12V VS = ±5V VS = ±3V 35 0 –5 –15 –15 –10 –5 0 5 10 COMMON-MODE VOLTAGE VGAIN (V) 15 06228-011 –10 –20 –40 –60 –80 –100 –120 –140 –160 –180 –200 –220 –0.8 Figure 11. Gain vs. Common-Mode Voltage at VGAIN T T T T T = +125°C = +85°C = +25°C = –40°C = –55°C –0.6 –0.4 –0.2 0 0.2 VGAIN (V) 0.4 0.6 Figure 14. Output Offset Voltage vs. VGAIN for Various Values of Temperature (T) Rev. D | Page 8 of 28 0.8 06228-014 45 GAIN (dB) GAIN ERROR (dB) 1.0 Data Sheet AD8336 20 50 40 –20 30 –60 20 0V 10 –0.2V GAIN (dB) –40 –80 –100 +0.2V 0 –120 –0.5V –140 –10 –0.7V –160 –200 –0.8 VS = ±12V VS = ±5V VS = ±3V –20 –0.4 –0.6 –0.2 0 0.2 VGAIN (V) 0.4 0.6 0.8 –30 100k 50 SAMPLE SIZE = 60 UNITS VGAIN = 0.7V VGAIN = +0.7V +0.5V 30 10 +0.2V GAIN (dB) % OF UNITS 20 0 30 –200 –160 –120 –80 –40 OUTPUT OFFSET (mV) 0 40 80 0V 10 –0.2V 0 SAMPLE SIZE = 60 UNITS VGAIN = 0V 20 100M 200M 40 20 –240 10M FREQUENCY (Hz) Figure 18. Frequency Response for Various Values of VGAIN (See Figure 57) Figure 15. Output Offset Voltage vs. VGAIN for Three Values of Supply Voltage (VS) 30 1M 06228-018 –180 06228-015 OUTPUT OFFSET VOLTAGE (mV) VGAIN = +0.7V +0.5V 0 –0.5V –10 –0.7V –20 10 –20 –16 –12 –8 –4 OUTPUT OFFSET (mV) 0 4 06228-016 –24 8 Figure 16. Output Offset Histogram 1M 10M FREQUENCY (Hz) 100M 200M 06228-019 LOW POWER MODE –30 100k 0 Figure 19. Frequency Response for Various Values of VGAIN, Low Power Mode (See Figure 57) 70 50 60 UNITS 60 VGAIN = +0.7V +0.5V 40 40 GAIN (dB) 30 20 30 +0.2V 0V –0.2V 20 0 16.30 16.35 16.40 16.45 INTERCEPT (dB) 16.50 16.55 –0.7V PREAMP GAIN = 20× –10 100k 1M 0 16.25 –0.5V Figure 17. Intercept Histogram 10M FREQUENCY (Hz) 100M 200M Figure 20. Frequency Response for Various Values of VGAIN When the Preamplifier Gain is 20× (See Figure 57) Rev. D | Page 9 of 28 06228-020 10 10 06228-017 % OF UNITS 50 AD8336 Data Sheet 50 30 VGAIN = +0.7V +0.5V 40 25 30 GAIN = –19× 20 20 15 GAIN (dB) GAIN (dB) +0.2V 0V 10 –0.2V GAIN = –3× 10 0 5 –0.5V –10 0 –20 –5 PREAMP GAIN = –3× 1M 10M FREQUENCY (Hz) 100M 200M –10 100k 06228-021 –30 100k VS = ±12V VS = ±5V VS = ±3V 1M 10M FREQUENCY (Hz) 100M 500M 06228-024 –0.7V Figure 24. Preamplifier Frequency Response for Three Values of Supply Voltage (VS) When the Inverting Gain Value is −3× or −19× (See Figure 69) Figure 21. Frequency Response for Various Values of VGAIN When the Preamplifier Gain is −3× (See Figure 69 and Figure 57) 20 25 PREAMP GAIN = 20× PREAMP GAIN = 4× VGAIN = 0V 20 15 GROUP DELAY (ns) 10 5 0 5 CL = CL = CL = CL = 47pF 22pF 10pF 0pF –10 100k 1M 10M FREQUENCY (Hz) 100M 200M 0 1M 06228-022 –5 10 Figure 22. Frequency Response for Various Values of Load Capacitance (CL) (See Figure 57) 10M FREQUENCY (Hz) 100M 06228-025 GAIN (dB) 15 Figure 25. Group Delay vs. Frequency for Preamplifier Gains of 4× and 20× (See Figure 59) 1k 30 GAIN = 20× 25 100 GAIN (dB) 15 OUTPUT RESISTANCE (Ω) 20 GAIN = 4× 10 5 0 10 1 1M 10M FREQUENCY (Hz) 100M 500M 06228-023 –10 100k VS = ±12V VS = ±5V VS = ±3V Figure 23. Preamplifier Frequency Response for Three Values of Supply Voltage (VS) When the Preamplifier Gain is 4× or 20× (See Figure 58) Rev. D | Page 10 of 28 0.01 100k 1M 10M FREQUENCY (Hz) 100M 500M Figure 26. Output Resistance vs. Frequency of the Preamplifier (See Figure 61) 06228-026 0.1 –5 Data Sheet AD8336 1k INPUT-REFERRED NOISE (nV/√Hz) 1k 10 1 0.1 VS = ±12V VS = ±5V VS = ±3V 10 PREAMP GAIN = 20× 1M 10M FREQUENCY (Hz) 100M 500M 1 –800 06228-027 0.01 100k PREAMP GAIN = 4× 100 –600 –400 –200 200 0 VGAIN (mV) 400 600 800 06228-030 OUTPUT RESISTANCE (Ω) 100 f = 5MHz Figure 30. Input-Referred Noise vs. VGAIN for Preamplifier Gains of 4× and 20× (See Figure 62) Figure 27. Output Resistance vs. Frequency of the VGA for Three Values of Supply Voltage (VS) (See Figure 61) 1000 6 f = 5MHz VGAIN = 0.7V 700 600 500 400 300 T T T T T 200 100 0 –800 –600 –400 –200 200 0 VGAIN (mV) 400 = +125°C = +85°C = +25°C = –40°C = –55°C 600 800 Figure 28. Output-Referred Noise vs. VGAIN at Various Temperatures (T) (See Figure 62) 5 4 3 2 1 VS = ±12V VS = ±5V VS = ±3V 0 100k 1M 10M FREQUENCY (Hz) 100M 06228-031 INPUT-REFERRED NOISE (nV/√Hz) 800 06228-028 OUTPUT-REFERRED NOISE (nV/√Hz) 900 Figure 31. Short-Circuit Input-Referred Noise vs. Frequency at Maximum Gain for Three Values of Supply Voltage (VS) (See Figure 62) 6 2400 5 2100 1800 1500 1200 900 T T T T T 600 300 0 –800 –600 –400 –200 200 0 VGAIN (mV) 400 = +125°C = +85°C = +25°C = –40°C = –55°C 600 800 Figure 29. Output-Referred Noise vs. VGAIN at Various Temperatures (T) When the Preamplifier Gain is 20× (See Figure 62) Rev. D | Page 11 of 28 VGAIN = 0.7V PREAMP GAIN = –3× 4 3 2 1 0 100k 1M 10M FREQUENCY (Hz) 100M Figure 32. Short-Circuit Input-Referred Noise vs. Frequency at Maximum Inverting Gain (See Figure 73) 06228-032 INPUT-REFERRED NOISE (nV/√Hz) f = 5MHz 2700 PREAMP GAIN = 20× 06228-029 OUTPUT-REFERRED NOISE (nV/√Hz) 3000 AD8336 –40 HARMONIC DISTORTION (dBc) –45 10 INPUT-REFERRED NOISE RS THERMAL NOISE ALONE 1 –50 HD2 –55 HD3 –60 10k 100 1k SOURCE RESISTANCE (Ω) –70 Figure 33. Input-Referred Noise vs. Source Resistance (See Figure 72) 15 20 30 35 25 LOAD CAPACITANCE (pF) 45 40 50 –20 50 SIMULATED DATA 40 30 50Ω SOURCE 10 –400 –200 0 200 VGAIN (mV) 400 600 800 Figure 34. Noise Figure vs. VGAIN (See Figure 63) –20 HARMONIC DISTORTION (dBc) HD2 –55 HD3 –60 –65 600 800 1.0k 1.2k 1.4k 1.6k 1.8k 2.0k 2.2k LOAD RESISTANCE (Ω) 06228-035 400 –200 HD2 f = 5MHz 0 200 VGAIN (mV) 400 600 800 OUTPUT SWING OF PREAMP LIMITS VGAIN LEVELS –40 –50 –60 –70 200 –400 –30 –50 0 HD2 @ 1MHz HD2 @ 10MHz HD3 @ 1MHz HD3 @ 10MHz Figure 37. Second and Third Harmonic Distortion vs. VGAIN at 1 MHz and 10 MHz (See Figure 64) VOUT = 2V p-p VGAIN = 0V f = 5MHz –45 –60 Figure 35. Harmonic Distortion vs. Load Resistance (See Figure 64) –80 –600 VOUT = 0.5V p-p VOUT = 1V p-p VOUT = 2V p-p VOUT = 4V p-p –400 –200 0 200 VGAIN (mV) 400 600 Figure 38. Second Harmonic Distortion vs. VGAIN for Four Values of Output Voltage (VOUT) (See Figure 64) Rev. D | Page 12 of 28 800 06228-038 –40 –50 –80 –600 06228-034 –600 –40 –70 UNTERMINATED 0 –800 –30 06228-037 HARMONIC DISTORTION (dBc) 60 20 OUTPUT SWING OF PREAMP LIMITS VGAIN TO 400mV VOUT = 1V p-p f = 10MHz NOISE FIGURE (dB) 10 Figure 36. Harmonic Distortion vs. Load Capacitance (See Figure 64) 70 –70 5 0 06228-036 –65 0.1 10 HARMONIC DISTORTION (dBc) VOUT = 2V p-p VGAIN = 0V f = 5MHz VGAIN = 0.7V 06228-033 INPUT-REFERRED NOISE (nV/√Hz) 100 Data Sheet Data Sheet –20 AD8336 40 HD3 f = 5MHz OUTPUT SWING OF PREAMP LIMITS MINIMUM USABLE VGAIN LEVELS 1MHz 500mV 1MHz 1V 10MHz 500mV 10MHz 1V 35 OUTPUT IP3 (dBm) 30 –40 –50 –60 25 20 15 10 –80 –600 –200 –400 5 0 200 VGAIN (mV) 400 600 800 VOUT = 1V p-p VGAIN = 0V COMPOSITE INPUTS SEPARATED BY 100kHz 0 –800 Figure 39. Third Harmonic Distortion vs. VGAIN for Four Values of Output Voltage (VOUT) (See Figure 64) –400 200 –200 0 VGAIN (mV) 400 600 800 Figure 42. Output-Referred IP3 (OIP3) vs. VGAIN at Two Frequencies and Two Input Levels (see Figure 76) 30 VOUT = 2V p-p VGAIN = 0V INPUT LEVEL LIMITED BY GAIN OF PREAMP VS = ±12V 20 –30 VS = ±5V 10 IP1dB (dBm) HARMONIC DISTORTION (dBc) –20 –600 06228-042 VOUT = 0.5V p-p VOUT = 1V p-p VOUT = 2V p-p VOUT = 4V p-p –70 06228-039 HARMONIC DISTORTION (dBc) –30 –40 HD2 –50 VS = ±3V 0 –10 –60 –20 10M FREQUENCY (Hz) 50M Figure 40. Harmonic Distortion vs. Frequency (See Figure 64) 0 –10 –30 –800 06228-040 –70 1M –600 –400 –200 200 0 VGAIN (mV) 400 600 800 06228-043 HD3 Figure 43. Input P1dB (IP1dB) vs. VGAIN at Three Power Supply Values (VS) (see Figure 74 and Figure 75) 3 VOUT = 1V p-p VGAIN = 0V TONES SEPARATED BY 100kHz 2 –20 1 VOLTAGE (V) –40 –50 0 VIN (V) VOUT (V) –1 –60 –70 –2 –90 1M 10M FREQUENCY (Hz) 100M –3 –100 0 100 TIME (ns) 200 300 Figure 44. Large-Signal Pulse Response of the Preamplifier (See Figure 65) Figure 41. IMD3 vs. Frequency (see Figure 76) Rev. D | Page 13 of 28 06228-044 –80 06228-041 IMD3 (dBc) –30 AD8336 Data Sheet 0.6 25 60 2.5 VGAIN = 0.7V OUTPUT 20 0 –0.2 VIN (mV) VOUT (mV) 0 –20 –0.4 –0.6 –100 –50 0 50 100 150 TIME (ns) 200 250 300 –60 350 5 0.5 0 –5 –0.5 –15 –1.5 –20 –2.0 –25 –100 20 60 50 200 250 300 –2.5 350 2.0 VGAIN = 0.7V VS= ±3V 15 0.2 1.5 10 1.0 5 0.5 0 0 INPUT –10 –40 –0.4 –15 0 50 100 150 TIME (ns) 200 250 300 –60 350 –20 –100 Figure 46. Inverting Gain Small-Signal Pulse Response (See Figure 70) 25 2.5 30 1.5 10 1.0 5 0.5 0 0 –5 –0.5 –10 –1.0 –1.5 INPUT OUTPUT WHEN PWRA = 0 OUTPUT WHEN PWRA = 1 –20 –25 –100 –50 0 50 100 150 TIME (ns) 200 50 100 150 200 TIME (ns) 250 300 350 VOUT (V) –2.0 400 3 VGAIN = 0.7V VS = ±5V 20 2 10 1 0 0 –10 INPUT CL = 0pF CL = 10pF CL = 22pF CL = 47pF* –1 –2 –20 –2.0 250 300 –2.5 350 06228-047 –15 VIN (mV) 15 VOUT (mV) 2.0 0 –1.5 Figure 49. Large-Signal Pulse Response for Various Values of Load Capacitance Using ±3 V Power Supplies (See Figure 65) VGAIN = 0.7V 20 –50 –1.0 *WITH 20Ω RESISTOR IN SERIES WITH OUTPUT. –30 50 200 100 150 250 –100 –50 0 TIME (ns) 300 –3 350 Figure 50. Large-Signal Pulse Response for Various Values of Load Capacitance Using ±5 V Power Supplies (See Figure 65) Figure 47. Large-Signal Pulse Response for Both Power Levels (See Figure 65) Rev. D | Page 14 of 28 06228-050 –50 06228-046 –0.6 –100 –0.5 INPUT CL = 0pF CL = 10pF CL = 22pF CL = 47pF 06228-049 –5 –20 VOUT (mV) 0 VIN (mV) 0 VOUT (mV) 20 –0.2 VIN (mV) 100 150 TIME (ns) 40 VGAIN = 0.7V PREAMP GAIN = –3× VIN (mV) 0 –50 Figure 48. Inverting Gain Large-Signal Pulse Response (See Figure 70) OUTPUT 0.4 –1.0 INPUT Figure 45. Noninverting Small-Signal Pulse Response for Both Power Levels (See Figure 65) 0.6 1.0 0 –10 –40 INPUT OUTPUT WHEN PWRA = 0 OUTPUT WHEN PWRA = 1 1.5 VGAIN = 0.7V PREAMP GAIN = –3× 10 20 06228-045 VIN (mV) 0.2 2.0 15 VOUT (mV) 40 06228-048 0.4 Data Sheet 3 10 20 2 0 10 1 0 0 –20 –30 –1 –40 –2 –20 *WITH 20Ω RESISTOR IN SERIES WITH OUTPUT –30 –100 –50 50 0 200 100 150 TIME (ns) 300 250 –50 –3 350 –60 100k Figure 51. Large-Signal Pulse Response for Various Values of Load Capacitance Using ±12 V Power Supplies (See Figure 65) 5M 0.5 VOUT VGAIN –0.5 –2.5 –0.5 0 0.5 1.0 TIME (µs) 1.5 2.0 06228-052 –1.5 5 0.5 4 0.3 3 0.2 2 0.1 1 0 0 –0.1 –1 –0.2 –2 OUTPUT VOLTAGE (V) VGAIN = 0.7V 0.4 –3 –0.3 VIN (V) VOUT (V) –4 –5 –6 –3 0 3 TIME (µs) 6 06228-053 –0.5 –9 20 LOW POWER 10 VS = ±12V VS = ±5V VS = ±3V 0 –65 –45 –25 –5 15 35 55 75 TEMPERATURE (°C) 95 115 135 Figure 55. IQ vs. Temperature for Three Values of Supply Voltage and High and Low Power (See Figure 68) Figure 52. Gain Response (See Figure 66) –0.4 HIGH POWER 30 Figure 53. VGA Overdrive Recovery (See Figure 67) Rev. D | Page 15 of 28 06228-055 QUIESCENT SUPPLY CURRENT (mA) 40 1.5 VOLTAGE (V) 1M FREQUENCY (Hz) Figure 54. PSRR vs. Frequency for Three Values of VGAIN (See Figure 71) 2.5 INPUT VOLTAGE (V) VGAIN = 0.7V VGAIN = 0V VGAIN = –0.7V 06228-054 –10 PSRR (dB) INPUT CL = 0pF CL = 10pF* CL = 22pF* CL = 47pF* PSRR VPOS VNEG –10 VOUT (mV) VGAIN = 0.7V VS = ±12V 06228-051 VIN (mV) 30 AD8336 AD8336 Data Sheet TEST CIRCUITS NETWORK ANALYZER NETWORK ANALYZER OUT OUT IN 50Ω IN 50Ω 50Ω AD8336 + 5 PREAMP – AD8336 453Ω 4 1 49.9Ω 8 9 12 5 1 11 8 301Ω 100Ω 9 12 11 301Ω 06228-056 VGAIN 453Ω + PREAMP – 06228-059 49.9Ω 4 50Ω 100Ω Figure 56. Gain vs. VGAIN and Gain Error vs. VGAIN Figure 59. Group Delay NETWORK ANALYZER OUT IN 50Ω 50Ω 453Ω AD8336 49.9Ω 4 + 5 PREAMP – AD8336 4 1 5 + PREAMP – 1 453Ω 50Ω DMM 12 11 OPTIONAL CL 301Ω NETWORK ANALYZER 50Ω 0Ω 453Ω NC 1 8 9 AD8336 NC + PREAMP – 301Ω CONFIGURE TO MEASURE Z-CONVERTED S22 IN 50Ω AD8336 5 + Figure 60. Offset Voltage IN 50Ω 4 11 ¯ NETWORK ANALYZER 49.9Ω 12 100Ω Figure 57. Frequency Response OUT 9 301Ω 06228-057 VGAIN 100Ω 8 06228-060 8 12 49.9Ω 4 + 5 PREAMP – 11 1 8 NC 12 11 301Ω 453Ω 100Ω 100Ω 06228-058 NC = NO CONNECT 9 0Ω NC NC = NO CONNECT Figure 61. Output Resistance vs. Frequency Figure 58. Frequency Response of the Preamplifier Rev. D | Page 16 of 28 06228-061 5 Data Sheet AD8336 OSCILLOSCOPE PULSE GENERATOR SPECTRUM ANALYZER POWER SPLITTER OUT CH2 CH1 50Ω 50Ω IN 50Ω AD8336 AD8336 4 5 1 OPTIONAL 20Ω 453Ω + PREAMP – 4 + PREAMP – 5 1 49.9Ω 8 8 12 9 11 0.7V 06228-065 100Ω 06228-062 VGAIN 100Ω 12 9 301Ω 11 301Ω Figure 62. Input-Referred Noise and Output-Referred Noise Figure 65. Pulse Response OSCILLOSCOPE PULSE FUNCTION GENERATOR GENERATOR NOISE FIGURE METER NOISE SOURCE DRIVE SINE WAVE SQUARE WAVE 5 50Ω 50Ω DIFFERENTIAL FET PROBE 11 0Ω AD8336 AD8336 49.9Ω (OR ∞) CH2 CH1 INPUT NOISE SOURCE 4 POWER SPLITTER 4 + PREAMP – 0Ω 1 49.9Ω 5 453Ω + PREAMP – 8 8 9 12 NC 1 9 12 301Ω 11 301Ω 06228-063 06228-066 100Ω VGAIN 100Ω NC = NO CONNECT Figure 66. Gain Response Figure 63. Noise Figure vs. VGAIN OSCILLOSCOPE ARBITRARY WAVEFORM GENERATOR SPECTRUM ANALYZER RL INPUT SIGNAL GENERATOR –20dB 50Ω LOW-PASS FILTER 5 1 + PREAMP – CL 8 9 12 453Ω 1 8 301Ω 11 301Ω 100Ω 50Ω 9 12 NC 11 0.7V 100Ω VGAIN 06228-067 5 4 49.9Ω + PREAMP – 06228-064 49.9Ω 50Ω AD8336 AD8336 4 CH2 CH1 POWER SPLITTER NC = NO CONNECT Figure 64. Harmonic Distortion Figure 67. VGA Overdrive Recovery Rev. D | Page 17 of 28 AD8336 Data Sheet POWER SUPPLIES CONNECTED TO NETWORK ANALYZER BIAS PORT NETWORK ANALYZER BENCH POWER SUPPLY DMM (+I) OUT IN 50Ω 50Ω 13 AD8336 4 5 + PREAMP – BYPASS CAPACITORS REMOVED FOR MEASUREMENT 1 VPOS OR VNEG AD8336 + PREAMP – 4 49.9Ω 9 8 12 5 10 11 1 DIFFERENTIAL FET PROBE 301Ω 9 8 DMM (–I) 12 11 06228-068 301Ω VGAIN 100Ω 06228-071 100Ω Figure 71. PSRR Figure 68. Supply Current NETWORK ANALYZER SPECTRUM ANALYZER OUT IN 50Ω 50Ω IN 50Ω 453Ω AD8336 AD8336 100Ω 100Ω 5 49.9Ω + PREAMP – + PREAMP – 4 1 5 8 12 9 1 11 9 8 301Ω 12 11 VGAIN 06228-069 301Ω 0.7V 100Ω Figure 69. Frequency Response, Inverting Gain 06228-072 4 Figure 72. Input-Referred Noise vs. Source Resistance SPECTRUM ANALYZER OSCILLOSCOPE PULSE GENERATOR POWER SPLITTER IN CH1 OUT CH2 50Ω 50Ω 50Ω AD8336 AD8336 4 5 + PREAMP – 1 453Ω 5 49.9Ω 1 8 301Ω 8 9 12 0.7V 9 12 11 301Ω 11 06228-070 100Ω 4 100Ω Figure 70. Pulse Response, Inverting Gain 0.7V 06228-073 100Ω + PREAMP – Figure 73. Short-Circuit Input-Referred Noise vs. Frequency Rev. D | Page 18 of 28 Data Sheet AD8336 SPECTRUM ANALYZER SIGNAL GENERATOR IN OUT 50Ω 50Ω OPTIONAL 20dB ATTENUATOR 22dB AD8336 49.9Ω 453Ω + PREAMP – 4 5 1 8 9 12 11 301Ω 06228-074 VGAIN 100Ω Figure 74. IP1dB vs. VGAIN SPECTRUM ANALYZER SIGNAL GENERATOR OUT IN 50Ω 50Ω –20dB AD8336 AMPLIFIER 49.9Ω 5 4 1 5 8 9 12 11 301Ω 453Ω + PREAMP – 1 8 9 12 11 301Ω 0.7V 100Ω VGAIN 100Ω 06228-075 4 AD8336 DUT 0Ω + PREAMP – Figure 75. IP1dB vs. VGAIN, High Signal Level Inputs SPECTRUM ANALYZER INPUT 50Ω –6dB COMBINER –6dB 4 +22dB –6dB 453Ω AD8336 DUT 49.9Ω 5 SIGNAL GENERATOR + PREAMP – 1 8 9 12 11 301Ω 100Ω Figure 76. IMD and OIP3 Rev. D | Page 19 of 28 VGAIN 06228-076 +22dB SIGNAL GENERATOR AD8336 Data Sheet THEORY OF OPERATION OVERVIEW PREAMPLIFIER The AD8336 is the first VGA designed for operation over exceptionally broad ranges of temperature and supply voltage. The performance has been characterized from temperatures extending from −55°C to +125°C, and supply voltages from ±3 V to ±12 V. It is ideal for applications requiring dc coupling, large output voltage swings, very large gain ranges, extreme temperature variations, or a combination thereof. The gain of the uncommitted voltage feedback preamplifier is set with external resistors. The combined preamplifier and VGA gain is specified in two ranges: −14 dB to +46 dB and 0 dB to 60 dB. Since the VGA gain is fixed at 34 dB (50×), the preamplifier gain is adjusted for gains of 12 dB (4×) and 26 dB (200×). The simplified block diagram is shown in Figure 77. The AD8336 includes a voltage feedback preamplifier, an amplifier with a fixed gain of 34 dB, a 60 dB attenuator, and various bias and interface circuitry. The independent voltage feedback operational amplifier can be used in noninverting and inverting configurations and functions as a preamplifier to the variable gain amplifier (VGA). If desired, the preamplifier output (PRAO) and VGA input (VGAI) pins provide for connection of an interstage filter to eliminate noise and offset. The bandwidth of the AD8336 is dc to 100 MHz with a gain range of 60 dB (−14 dB to +46 dB). For applications that require large supply voltages, a reduction in power is advantageous. The power reduction pin (PWRA) permits the power and bandwidth to be reduced by about half in such applications. PRAO VGAI 12dB INPP * + INPN PREAMP – –60dB TO 0dB ATTENUATOR AND GAIN 1.28kΩ CONTROL INTERFACE 34dB + _ RFB2 301Ω VOUT 4.48kΩ 91.43Ω RFB1 100Ω With low preamplifier gains between 2× and 4×, it can be desirable to reduce the high frequency gain with a shunt capacitor across RFB2 to ameliorate peaking in the frequency domain (see Figure 77). To maintain stability, the gain of the preamplifier must be 6 dB (2×) or greater. Typical of voltage feedback amplifier configurations, the gainbandwidth product of the AD8336 is fixed (at 600); therefore, the bandwidth decreases as the gain is increased beyond the nominal gain value of 4×. For example, if the preamplifier gain is increased to 20×, the bandwidth reduces by a factor of 5 to about 20 MHz. The −3 dB bandwidth of the preamplifier with a gain of 4× is about 150 MHz, and for the 20× gain is about 30 MHz. The preamplifier gain diminishes for an amplifier configured for inverting gain, using the same value of feedback resistors as for a noninverting amplifier, but the bandwidth remains unchanged. For example, if the noninverting gain is 4×, the inverting gain is −3×, but the bandwidth stays the same as in the noninverting gain of 4×. However, because the output-referred noise of the preamplifier is the same in both cases, the input-referred noise increases as the ratio of the two gain values increases. For the previous example, the input-referred noise increases by a factor of 4/3. The output swing of the preamplifier is the same as for the VGA. PWRA VPOS VNEG GPOS GNEG VCOM *OPTIONAL DEPEAKING CAPACITOR. SEE TEXT. 06228-077 BIAS Figure 77. Simplified Block Diagram To maintain low noise, the output stages of both the preamplifier and the VGA are capable of driving relatively small load resistances. However, at the largest supply voltages, the signal current can exceed safe operating limits for the amplifiers and, therefore, the load current must not exceed 50 mA. With a ±12 V supply and ±10 V output voltage at the preamplifier or VGA output, load resistances as low as 200 Ω are acceptable. For power supply voltages ≥ ±10 V, the maximum operating temperature range is derated to +85°C because the power can exceed safe limits (see the Absolute Maximum Ratings section). Because harmonic distortion products can increase for various combinations of low impedance loads and high output voltage swings, it is recommended that the user determine load and drive conditions empirically. VGA The architecture of the variable gain amplifier (VGA) section of the AD8336 is based on the Analog Devices, Inc., X-AMP (exponential amplifier), found in a wide variety of Analog Devices variable gain amplifiers. This type of VGA combines a ladder attenuator and interpolator, followed by a fixed-gain amplifier. The gain control interface is fully differential, permitting positive or negative gain slopes. Note that the common-mode voltage of the gain control inputs increases with increasing supply. The gain slope is 50 dB/V and the intercept is 16.4 dB when the nominal preamplifier gain is 4× (12 dB). The intercept changes with the preamplifier gain; for example, when the preamplifier gain is set to 20× (26 dB), the intercept becomes 30.4 dB. Pin VGAI is connected to the input of the ladder attenuator. The ladder ratio is R/2R and the nominal resistance is 320 Ω. To reduce preamplifier loading and large-signal dissipation, the input resistance at Pin VGAI is 1.28 kΩ. Safe current density and power dissipation levels are maintained even when large dc signals are applied to the ladder. Rev. D | Page 20 of 28 Data Sheet AD8336 The tap resistance of the resistors within the R/2R ladder is 640 Ω/3, or 213.3 Ω, and is the Johnson noise source of the attenuator. NOISE The noise of the AD8336 is dependent on the value of the VGA gain. At maximum VGAIN, the dominant noise source is the preamplifier, but it shifts to the VGA as VGAIN diminishes. SETTING THE GAIN The overall gain of the AD8336 is the sum (in decibels) or the product (magnitude) of the preamplifier gain and the VGA gain. The preamplifier gain is calculated as with any operational amplifier, as seen in the Applications Information section. It is most convenient to think of the device gain in exponential terms (that is, in decibels) since the VGA responds linearly in decibels with changes in control voltage VGAIN at the gain pins. 50 dB VGA Gain (dB) V GAIN (V) 4. 4 dB V where VGAIN = VGPOS − VGNEG. The gain and gain range of the VGA are both fixed at 34 dB and 60 dB, respectively; thus, the composite device gain is changed by adjusting the preamplifier gain. For a preamplifier gain of 12 dB (4×), the composite gain is −14 dB to +46 dB. Therefore, the calculation for the composite gain (in decibels) is Composite Gain = GPRA + [VGAIN (V) × 49.9 dB/V] + 4.4 dB For example, the midpoint gain when the preamplifier gain is 12 dB is 12 dB + [0 V × 49.9 dB/V] + 4.4 dB = 16.4 dB Figure 3 is a plot of gain in decibels vs. VGAIN in millivolts, when the preamplifier gain is 12 dB (4×). Note that the computed result closely matches the plot of actual gain. In Figure 3, the gain slope flattens at the limits of the VGAIN input. The gain response is linear in dB over the center 80% of the control range of the device. Figure 78 shows the ideal gain characteristics for the VGA stage gain, the composite gain, and the preamplifier gain. 60 GAIN CHARACTERISTICS COMPOSITE GAIN VGA STAGE GAIN 50 GAIN (dB) 40 30 FOR PREAMP GAIN = 26dB FOR PREAMP GAIN = 12dB FOR PREAMP GAIN = 6dB –0.3 –0.1 0.1 VGAIN (V) 0.3 0.5 Figure 78. Ideal Gain Characteristics of the AD8336 0.7 06228-078 –20 –0.5 At other than maximum gain, the noise of the VGA is determined from the output noise. The noise in the center of the gain range is about 150 nV/Hz. Because the gain of the fixed-gain amplifier that is part of the VGA is 50×, the VGA input-referred noise is approximately 3 nV/Hz, the same value as the preamplifier and VGA combined. This is expected since the input-referred noise is the same at the input of the attenuator at maximum gain. However, the noise referred to the VGAI pin (the preamplifier output) increases by the amount of attenuation through the ladder network. The noise at any point along the ladder network is primarily composed of the ladder resistance noise, the noise of the input devices, and the feedback resistor network noise. The ladder network and the input devices are the largest noise sources. Extensive cancellation circuitry included in the variable gain amplifier section minimizes locally generated offset voltages. However, when operated at very large values of gain, dc voltage errors at the output can still result from small dc input voltages. When configured for the nominal gain range of −14 dB to +46 dB, the maximum gain is 200× and an offset of only 100 μV at the input generates 20 mV at the output. 10 –30 –0.7 Using the values listed in Table 4, the total noise of the AD8336 is slightly less than 3 nV/Hz, referred to the input. Although the input noise referred to the VGA is 3.1 nV/Hz, the inputreferred noise at the preamplifier is 0.77 nV/Hz when divided by the preamplifier gain of 4×. OFFSET VOLTAGE 20 –10 Noise Voltage (nV/√Hz) 2.6 0.96 0.55 0.77 At minimum gain, the output noise increases slightly to about 180 nV/Hz because of the finite structure of the X-AMP. USABLE GAIN RANGE OF AD8336 0 Table 4. AD8336 Noise Components for Preamplifier Gain = 4× Noise Component Op Amp (Gain = 4×) RFB1 = 100 Ω RFB2 = 301 Ω VGA The gain equation for the VGA is 70 The input-referred noise at the highest VGA gain and a preamplifier gain of 4×, with RFB1 = 100 Ω and RFB2 = 301 Ω, is 3 nV/Hz and is determined by the preamplifier and the gain setting resistors. See Table 4 for the noise components for the preamplifier. The primary source for dc offset errors is the preamplifier; ac coupling between the PRAO and VGAI pins is the simplest solution. In applications where dc coupling is essential, a compensating current can be injected at the INPN input (Pin 5) to cancel preamplifier offset. The direction of the compensating current depends on the polarity of the offset voltage. Rev. D | Page 21 of 28 AD8336 Data Sheet APPLICATIONS INFORMATION AMPLIFIER CONFIGURATION Circuit Configuration for Noninverting Gain The AD8336 amplifiers can be configured in various options. In addition to the 60 dB gain range variable gain stage, an uncommitted voltage gain amplifier is available to the user as a preamplifier. The preamplifier connections are separate to enable noninverting or inverting gain configurations or the use of interstage filtering. The AD8336 can be used as a cascade connected VGA with preamp input, as a standalone VGA, or as a standalone preamplifier. This section describes some of the possible applications. The noninverting configuration is shown in Figure 80. The preamplifier gain is described by the classical operational amplifier gain equation: INPN 5 VGAI 8 9 + PREAMP – ATTENUATOR –60dB TO 0dB 34dB 1 VOUT AD8336 R FB 2 The practical gain limits for this amplifier are 6 dB to 26 dB. The gain bandwidth product is about 600 MHz, so at 150 MHz, the maximum achievable gain is 12 dB (4×). The minimum gain is established internally by fixed loop compensation and is 6 dB (2×). This amplifier is not designed for unity-gain operation. Table 5 shows the gain and bandwidth for the noninverting gain configuration. INPP PWRA 2 INPN GAIN CONTROL INTERFACE BIAS 1 R FB 1 RFB1 100Ω AD8336 5 RFB2 301Ω 13 3 11 12 VNEG VPOS VCOM GPOS GNEG 06228-079 8 10 PREAMPLIFIER 4 –60dB TO 0dB GAIN = 12dB 1 VOUT PWRA VNEG VCOM VPOS VGAI 9 2 10 –5V Figure 79. Application Block Diagram 34dB PRAO 3 13 +5V 06228-080 INPP 4 PRAO Gain Figure 80. Circuit Configuration for Noninverting Gain PREAMPLIFIER While observing just a few constraints, the uncommitted voltage feedback preamplifier of the AD8336 can be connected in a variety of standard high frequency operational amplifier configurations. The amplifier is optimized for a gain of 4× (12 dB) and has a gain bandwidth product of 600 MHz. At a gain of 4×, the bandwidth is 150 MHz. The preamplifier gain can be adjusted to a minimum gain of 2×; however, there will be a small peak in the response at high frequencies. At higher preamplifier gains, the bandwidth diminishes proportionally in conformance to the classical voltage gain amplifier GBW relationship. While setting the overall gain of the AD8336, the user must consider the input-referred offset voltage of the preamplifier. Although the offset of the attenuator and postamplifier are almost negligible, the preamplifier offset voltage, if uncorrected, is increased by the combined gain of the preamplifier and postamplifier. Therefore, for a maximum gain of 60 dB, an input offset voltage of only 200 μV results in an error of 200 mV at the output. The preamplifier output reliably sources and sinks currents up to 50 mA. When using ±5 V power supplies, the suggested sum of the output resistor values is 400 Ω total for the optimal tradeoff between distortion and noise. Much of the low gain value device characterization was performed with resistor values of 301 Ω and 100 Ω, resulting in a preamplifier gain of 12 dB (4×). With supply voltages between ±5 V and ±12 V, the sum of the output resistance must be increased accordingly; a total resistance of 1 kΩ is recommended. Larger resistance values, subject to a trade-off in higher noise performance, can be used if circuit power and load driving is an issue. When considering the total power dissipation, remember that the input ladder resistance of the VGA is part of the preamplifier load. Table 5. Gain and Bandwidth for Noninverting Preamplifier Configuration Preamplifier Gain Numerical dB 4× 12 8× 18 16× 24 20× 26 Rev. D | Page 22 of 28 Preamplifier BW (MHz) 150 60 30 25 Composite Gain (dB) −14 to +46 −8 to +52 −2 to +58 0 to +60 Data Sheet AD8336 Circuit Configuration for Inverting Gain USING THE POWER ADJUST FEATURE The preamplifier can also be used in an inverting configuration, as shown in Figure 81. The AD8336 has the provision to operate at lower power with a trade-off in bandwidth. The power reduction applies to the preamplifier and the VGA sections, and the bandwidth is reduced equally between them. Reducing the power is particularly useful when operating with higher supply voltages and lower values of output loading that otherwise stresses the output amplifiers. When Pin PWRA is grounded, the amplifiers operate in their default mode, and the combined 3 dB bandwidth is 80 MHz with the preamplifier gain adjusted to 4×. When the voltage on Pin PWRA is between 1.2 V and 5 V, the power is reduced by approximately half and the 3 dB bandwidth reduces to approximately 35 MHz. The voltage at Pin PWRA must not exceed 5 V. AD8336 GAIN = 9.6dB INPN RFB1 100Ω RFB2 301Ω PREAMPLIFIER 4 + 5 – –60dB TO 0dB 8 34dB 1 VOUT PRAO VGAI PWRA VNEG VCOM VPOS 9 2 10 –5V 3 13 +5V 06228-081 INPP Figure 81. Circuit Configuration for Inverting Gain The considerations regarding total resistance vs. distortion, noise, and power that were noted in the noninverting case also apply in the inverting case, except that the amplifier can be operated at unity inverting gain. The signal gain is reduced while the noise gain is the same as for the noninverting configuration: Signal Gain RFB2 RFB1 and Noise Gain RFB2 1 RFB1 DRIVING CAPACITIVE LOADS The output stages of the AD8336 are stable with capacitive loads up to 47 pF for a supply voltage of ±3 V and with capacitive loads up to 10 pF for supply voltages up to ±8 V. For larger combined values of load capacitance and/or supply voltage, a 20 Ω series resistor is recommended for stability. The influence of capacitance and supply voltage are shown in Figure 50 and Figure 51, where representative combinations of load capacitance and supply voltage requiring a 20 Ω resistor are marked with an asterisk. No resistor is required for the ±3 V plots in Figure 49, but a resistor is required for most of the ±12 V plots in Figure 51. Rev. D | Page 23 of 28 AD8336 Data Sheet EVALUATION BOARD An evaluation board, AD8336-EVALZ, is available online for the AD8336. Figure 82 is a photo of the board. The board is shipped from the factory configured for a noninverting preamplifier gain of 4×. To change the value of the gain of the preamplifier or to change the gain polarity to inverting, alter the component values or install components in the alternate locations provided. All components are standard 0603 size, and the board is compliant with RoHS requirements. Table 6 shows the components to be removed and added to change the amplifier configuration to inverting gain. Remove R4, R7 06228-083 Table 6. Component Changes for Inverting Configuration Install R5, R6 Figure 82. AD8336 Evaluation Board The AD8336 features differential inputs for the gain control, permitting nonzero or floating gain control inputs. To avoid any delay in making the board operational, the gain input circuit is shipped with Pin GNEG connected to ground via a 0 Ω resistor in the R17 location. The user can adjust the gain of the device by driving the GPOS test loop with a power supply or voltage reference. Optional resistor networks R15/R17 and R13/R14 provide fixed-gain bias voltages at Pin GNEG and Pin GPOS for non-zero common-mode voltages. The gain control can also be driven with an active input such as a ramp. Provision is made for an optional SMA connector at PRVG for monitoring the preamplifier output or for driving the VGA from an external source. Remove the 0 Ω resistor at R9 to isolate the preamplifier from an external generator. The capacitor at Location C1 limits the bandwidth of the preamplifier. 06228-084 OPTIONAL CIRCUITRY Figure 83. Component Side Copper BOARD LAYOUT CONSIDERATIONS 06228-085 The evaluation board uses four layers, with power and ground planes located between two conductor layers. This arrangement is highly recommended for customers, and several views of the board are provided as reference for board layout details. When laying out a printed circuit board for the AD8336, remember to provide a pad beneath the device to solder the exposed pad of the matching device. The pad in the board must have at least five vias to provide a thermal path for the chip scale package. Unlike leaded devices, the thermal pad is the primary means to remove heat dissipated within the device. Figure 84. Secondary Side Copper Rev. D | Page 24 of 28 AD8336 06228-086 Data Sheet 06228-087 Figure 85. Component Side Silkscreen 06228-088 Figure 86. Internal Ground Plane Copper Figure 87. Internal Power Plane Copper Rev. D | Page 25 of 28 AD8336 Data Sheet VPOS GND GND1 GND2 GND3 + L2 120nH R1 0Ω VOUT VOUTL VP R16 4.99kΩ CR1 5.1V 16 15 14 13 NC NC NC VPOS 1 LOW R3 0Ω VIN R2 49.9Ω C3 0.1µF VOUTD C8 0.1µF NORM VIN1 VOUT 3 GNEG R4 0Ω 4 GPOS AD8336 VCOM VNEG INPP VGAI R7 100Ω GNEG R17 0Ω 12 R14 11 GPOS C7 1nF 10 C5 9 0.1µF INPN NC NC PRAO 5 6 7 8 R8 301Ω R15 C6 1nF U1 POWER 2 PWRA R6 R5 VP L1 120nH + R11 0Ω R9 0Ω R13 R12 0Ω C2 10µF 25V –VS PRVG R10 49.9Ω C1 NC = NO CONNECT. DO NOT CONNECT TO THIS PIN. Figure 88. AD8336-EVALZ Schematic Shown as Shipped, Configured for a Noninverting Gain of 4× Rev. D | Page 26 of 28 06228-082 C4 10µF 35V Data Sheet AD8336 OUTLINE DIMENSIONS DETAIL A (JEDEC 95) 0.35 0.30 0.25 13 0.65 BSC PIN 1 INDIC ATOR AREA OPTIONS (SEE DETAIL A) 16 1 12 2.25 2.10 SQ 1.95 EXPOSED PAD 9 TOP VIEW PKG-004025/5112 0.80 0.75 0.70 SEATING PLANE 0.70 0.60 0.50 4 5 8 BOTTOM VIEW 0.05 MAX 0.02 NOM COPLANARITY 0.08 0.203 REF 0.25 MIN FOR PROPER CONNECTION OF THE EXPOSED PAD, REFER TO THE PIN CONFIGURATION AND FUNCTION DESCRIPTIONS SECTION OF THIS DATA SHEET. COMPLIANT TO JEDEC STANDARDS MO-220-WGGC. 04-15-2016-A PIN 1 INDICATOR 4.10 4.00 SQ 3.90 Figure 89. 16-Lead Lead Frame Chip Scale Package [LFCSP] 4 mm × 4 mm Body and 0.75 mm Package Height (CP-16-23) Dimensions shown in millimeters ORDERING GUIDE Model 1 AD8336ACPZ-R7 AD8336ACPZ-RL AD8336ACPZ-WP AD8336-EVALZ 1 Temperature Range −40°C to +85°C −40°C to +85°C −40°C to +85°C Package Description 16-Lead Lead Frame Chip Scale Package [LFCSP] 16-Lead Lead Frame Chip Scale Package [LFCSP] 16-Lead Lead Frame Chip Scale Package [LFCSP] Evaluation Board Z = RoHS Compliant Part. Rev. D | Page 27 of 28 Package Option CP-16-23 CP-16-23 CP-16-23 AD8336 Data Sheet NOTES ©2006–2016 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D06228-0-5/16(D) Rev. D | Page 28 of 28