Low Noise, 90 MHz Variable Gain Amplifier AD603 Data Sheet The decibel gain is linear in dB, accurately calibrated, and stable over temperature and supply. The gain is controlled at a high impedance (50 MΩ), low bias (200 nA) differential input; the scaling is 25 mV/dB, requiring a gain control voltage of only 1 V to span the central 40 dB of the gain range. An overrange and underrange of 1 dB is provided whatever the selected range. The gain control response time is less than 1 μs for a 40 dB change. FEATURES Linear-in-dB gain control Pin-programmable gain ranges −11 dB to +31 dB with 90 MHz bandwidth 9 dB to 51 dB with 9 MHz bandwidth Any intermediate range, for example −1 dB to +41 dB with 30 MHz bandwidth Bandwidth independent of variable gain 1.3 nV/√Hz input noise spectral density ±0.5 dB typical gain accuracy The differential gain control interface allows the use of either differential or single-ended positive or negative control voltages. Several of these amplifiers may be cascaded and their gain control gains offset to optimize the system SNR. The AD603 can drive a load impedance as low as 100 Ω with low distortion. For a 500 Ω load in shunt with 5 pF, the total harmonic distortion for a ±1 V sinusoidal output at 10 MHz is typically −60 dBc. The peak specified output is ±2.5 V minimum into a 500 Ω load. APPLICATIONS RF/IF AGC amplifiers Video gain controls A/D range extensions Signal measurements The AD603 uses a patented proprietary circuit topology—the X-AMP®. The X-AMP comprises a variable attenuator of 0 dB to −42.14 dB followed by a fixed-gain amplifier. Because of the attenuator, the amplifier never has to cope with large inputs and can use negative feedback to define its (fixed) gain and dynamic performance. The attenuator has an input resistance of 100 Ω, laser trimmed to ±3%, and comprises a 7-stage R-2R ladder network, resulting in an attenuation between tap points of 6.021 dB. A proprietary interpolation technique provides a continuous gain control function that is linear in dB. GENERAL DESCRIPTION The AD603 is a low noise, voltage-controlled amplifier for use in RF and IF AGC systems. It provides accurate, pin-selectable gains of −11 dB to +31 dB with a bandwidth of 90 MHz or +9 dB to 51+ dB with a bandwidth of 9 MHz. Any intermediate gain range may be arranged using one external resistor. The input referred noise spectral density is only 1.3 nV/√Hz, and power consumption is 125 mW at the recommended ±5 V supplies. The AD603 is specified for operation from −40°C to +85°C. FUNCTIONAL BLOCK DIAGRAM SCALING REFERENCE PRECISION PASSIVE INPUT ATTENUATOR FIXED-GAIN AMPLIFIER GPOS VOUT VG GNEG 6.44kΩ* AD603 GAINCONTROL INTERFACE FDBK 694Ω* 0dB VINP –6.02dB R 2R –12.04dB –18.06dB –24.08dB R 2R R 2R R 2R –30.1dB R 2R –36.12dB –42.14dB R 2R R R 20Ω* 00539-001 COMM R-2R LADDER NETWORK *NOMINAL VALUES. Figure 1. Rev. K 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 www.analog.com Fax: 781.461.3113 ©1993–2012 Analog Devices, Inc. All rights reserved. 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Product Selection Guide • Variable Gain Amplifier Selection Table Tutorials • Design and Operation of Automatic Gain Control Loops for Receivers in Modern Communication Systems This page is dynamically generated by Analog Devices, Inc., and inserted into this data sheet. A dynamic change to the content on this page will not trigger a change to either the revision number or the content of the product data sheet. This dynamic page may be frequently modified. AD603 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 The Gain Control Interface ....................................................... 13 Applications ....................................................................................... 1 General Description ......................................................................... 1 Programming the Fixed-Gain Amplifier Using Pin Strapping...................................................................................... 13 Functional Block Diagram .............................................................. 1 Using the AD603 in Cascade ........................................................ 15 Revision History ............................................................................... 2 Sequential Mode (Optimal SNR) ............................................. 15 Specifications..................................................................................... 3 Parallel Mode (Simplest Gain Control Interface) .................. 16 Absolute Maximum Ratings............................................................ 4 Low Gain Ripple Mode (Minimum Gain Error) ................... 17 ESD Caution .................................................................................. 4 Applications Information .............................................................. 18 Pin Configurations and Function Descriptions ........................... 5 A Low Noise AGC Amplifier .................................................... 18 Typical Performance Characteristics ............................................. 6 Caution ........................................................................................ 19 Test Circuits ..................................................................................... 11 Evaluation Board ............................................................................ 20 Theory of Operation ...................................................................... 12 Outline Dimensions ....................................................................... 22 Noise Performance ..................................................................... 12 Ordering Guide .......................................................................... 23 REVISION HISTORY 4/12—Rev. J to Rev. K Changes to Table 1 ............................................................................ 3 Added Figure 10 and Figure 11; Renumbered Sequentially ....... 7 Added Test Circuits Section .......................................................... 11 Moved Figure 29 and Figure 30 .................................................... 11 12/11—Rev. I to Rev. J Changes to Figure 1 ......................................................................... 1 Changes to Evaluation Board Section .......................................... 19 Changes to Figure 48 Through Figure 50 .................................... 19 Changes to Figure 51 Through Figure 54 .................................... 20 Added Figure 57.............................................................................. 22 5/07—Rev. G to Rev. H Changes to Layout .......................................................................... 14 Changes to Layout .......................................................................... 15 Changes to Layout .......................................................................... 16 Inserted Evaluation Board Section, and Figure 48 to Figure 51 .......................................................................................... 19 Inserted Figure 52 and Table 4 ...................................................... 20 Changes to Ordering Guide .......................................................... 21 3/05—Rev. F to Rev. G Updated Format .................................................................. Universal Change to Features ............................................................................1 Changes to General Description .....................................................1 Change to Figure 1 ............................................................................1 Changes to Specifications .................................................................3 New Figure 4 and Renumbering Subsequent Figures ..................6 Change to Figure 10 ..........................................................................7 Change to Figure 23 ..........................................................................9 Change to Figure 29 ....................................................................... 12 Updated Outline Dimensions ....................................................... 20 4/04—Rev. E to Rev. F Changes to Specifications .................................................................2 Changes to Ordering Guide .............................................................3 8/03—Rev. D to Rev E Updated Format .................................................................. Universal Changes to Specifications .................................................................2 Changes to TPCs 2, 3, 4 ....................................................................4 Changes to Sequential Mode (Optimal S/N Ratio) section .........9 Change to Figure 8 ......................................................................... 10 Updated Outline Dimensions ....................................................... 14 Rev. K | Page 2 of 24 Data Sheet AD603 SPECIFICATIONS @ TA = 25°C, VS = ±5 V, –500 mV ≤ VG ≤ +500 mV, GNEG = 0 V, –10 dB to +30 dB gain range, RL = 500 Ω, and CL = 5 pF, unless otherwise noted. Table 1. Parameter INPUT CHARACTERISTICS Input Resistance Input Capacitance Input Noise Spectral Density 1 Noise Figure 1 dB Compression Point Peak Input Voltage OUTPUT CHARACTERISTICS −3 dB Bandwidth Slew Rate Peak Output 2 Output Impedance Output Short-Circuit Current Group Delay Change vs. Gain Group Delay Change vs. Frequency Differential Gain Differential Phase Total Harmonic Distortion Third-Order Intercept ACCURACY Gain Accuracy, f = 100 kHz; Gain (dB) = (40 VG + 10) dB TMIN to TMAX Gain, f = 10.7 MHz Output Offset Voltage 3 TMIN to TMAX Output Offset Variation vs. VG TMIN to TMAX GAIN CONTROL INTERFACE Gain Scaling Factor TMIN to TMAX GNEG, GPOS Voltage Range 4 Input Bias Current Input Offset Current Differential Input Resistance Response Rate POWER SUPPLY Specified Operating Range Quiescent Current TMIN to TMAX Conditions Min Typ Max Unit Pin 3 to Pin 4 97 100 2 1.3 8.8 −11 ±1.4 103 Ω pF nV/√Hz dB dBm V Input short-circuited f = 10 MHz, gain = maximum, RS = 10 Ω f = 10 MHz, gain = maximum, RS = 10 Ω VOUT = 100 mV rms RL ≥ 500 Ω RL ≥ 500 Ω f ≤ 10 MHz ±2.5 f = 3 MHz; full gain range VG = 0 V; f = 1 MHz to 10 MHz f = 10 MHz, VOUT = 1 V rms f = 40 MHz, gain = maximum, RS = 50 Ω −500 mV ≤ VG ≤ +500 mV VG = -0.5 V VG = 0.0 V VG = 0.5 V VG = 0 V 90 275 ±3.0 2 50 ±2 ±2 0.2 0.2 −60 15 −1 −1.5 −10.3 +9.5 +29.3 ±0.5 39.4 38 38.7 −1.2 50 40 −9.0 +10.5 +30.3 −500 mV ≤ VG ≤ +500 mV 100 kHz 10.7 MHz Pin 1 to Pin 2 Full 40 dB gain change 39.3 100 10 50 80 ±4.75 12.5 1 ±2 MHz V/µs V Ω mA ns ns % Degree dBc dBm +1 +1.5 −8.0 +11.5 +31.3 20 30 20 30 dB dB dB dB dB mV mV mV mV 40.6 42 39.9 +2.0 250 dB/V dB/V dB/V V nA nA MΩ dB/µs ±6.3 17 20 V mA mA Typical open or short-circuited input; noise is lower when system is set to maximum gain and input is short-circuited. This figure includes the effects of both voltage and current noise sources. Using resistive loads of 500 Ω or greater or with the addition of a 1 kΩ pull-down resistor when driving lower loads. 3 The dc gain of the main amplifier in the AD603 is ×35.7; therefore, an input offset of 100 µV becomes a 3.57 mV output offset. 4 GNEG and GPOS, gain control, and voltage range are guaranteed to be within the range of −VS + 4.2 V to +VS − 3.4 V over the full temperature range of −40°C to +85°C. 2 Rev. K | Page 3 of 24 AD603 Data Sheet ABSOLUTE MAXIMUM RATINGS Table 2. Parameter Supply Voltage ±VS Internal Voltage VINP (Pin 3) GPOS, GNEG (Pin 1 and Pin2) Internal Power Dissipation Operating Temperature Range AD603A AD603S Storage Temperature Range Lead Temperature (Soldering, 60 sec) Rating ±7.5 V ±2 V Continuous ±VS for 10 ms ±VS 400 mW Table 3. Thermal Characteristics Package Type 8-Lead SOIC 8-Lead CERDIP ESD CAUTION −40°C to +85°C −55°C to +125°C −65°C to +150°C 300°C Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Rev. K | Page 4 of 24 θJA 155 140 θJC 33 15 Unit °C/W °C/W Data Sheet AD603 AD603 8 VPOS GPOS 1 7 VOUT GNEG 2 6 VNEG VINP 3 TOP VIEW COMM 4 (Not to Scale) 5 FDBK VINP 3 00539-002 GPOS 1 GNEG 2 COMM 4 Figure 2. 8-Lead SOIC Pin Configuration Mnemonic GPOS GNEG VINP COMM FDBK VNEG VOUT VPOS 8 VPOS 7 VOUT TOP VIEW 6 VNEG (Not to Scale) 5 FDBK Figure 3. 8-Lead CERDIP Pin Configuration Table 4. Pin Function Descriptions Pin No. 1 2 3 4 5 6 7 8 AD603 00539-003 PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS Description Gain Control Input High (Positive Voltage Increases Gain). Gain Control Input Low (Negative Voltage Increases Gain). Amplifier Input. Amplifier Ground. Connection to Feedback Network. Negative Supply Input. Amplifier Output. Positive Supply Input. Rev. K | Page 5 of 24 AD603 Data Sheet TYPICAL PERFORMANCE CHARACTERISTICS @ TA = 25°C, VS = ±5 V, –500 mV ≤ VG ≤ +500 mV, GNEG = 0 V, –10 dB to +30 dB gain range, RL = 500 Ω, and CL = 5 pF, unless otherwise noted. 225 3 180 2 135 1 0 GAIN (dB) 20 GAIN (dB) 90 GAIN 10.7MHz 10 100kHz 0 –0.4 –0.2 0 VG (V) 0.2 0.4 0.6 45 –1 0 PHASE –2 –45 –3 –90 –4 –135 –5 –180 –225 –6 100k 00539-004 –10 –0.6 PHASE (Degrees) 30 4 Figure 4. Gain vs. VG at 100 kHz and 10.7 MHz 1M 10M FREQUENCY (Hz) 00539-007 40 100M Figure 7. Frequency and Phase Response vs. Gain (Gain = 10 dB, PIN = −30 dBm) 2.5 4 225 2.0 3 180 2 135 45MHz 1.5 90 0 10.7MHz 0.5 0 455kHz PHASE (Degrees) GAIN 70MHz GAIN (dB) GAIN ERROR (dB) 1 1.0 45 –1 0 PHASE –2 –45 –3 –90 –4 –135 –5 –180 70MHz –1.0 –0.3 –0.2 –0.1 0 0.1 0.2 GAIN VOLTAGE (V) 0.3 0.4 0.5 4 225 3 180 2 135 –3 –90 –4 –135 –5 –180 –225 1M 10M FREQUENCY (Hz) 100M GROUP DELAY (ns) –45 PHASE (Degrees) 0 PHASE –2 –6 100k 100M 7.4 7.2 7.0 6.8 6.6 00539-006 GAIN (dB) 45 –1 10M FREQUENCY (Hz) 7.6 90 GAIN 0 1M Figure 8. Frequency and Phase Response vs. Gain (Gain = 30 dB, PIN = −30 dBm) Figure 5. Gain Error vs. Gain Control Voltage at 455 kHz, 10.7 MHz, 45 MHz, 70 MHz 1 –225 –6 100k 6.4 –0.6 –0.4 –0.2 0 0.2 GAIN CONTROL VOLTAGE (V) 0.4 Figure 9. Group Delay vs. Gain Control Voltage Figure 6. Frequency and Phase Response vs. Gain (Gain = −10 dB, PIN = −30 dBm) Rev. K | Page 6 of 24 0.6 00539-009 –0.4 00539-005 –1.5 –0.5 00539-008 –0.5 Data Sheet 553 PIECE SAMPLE SIZE VOS AT 10dB GAIN VOS VS VGAIN 50 10dB/DIV 40 30 20 0 2 4 6 8 10 12 14 16 18 20 OFFSET VOLTAGE (mV) Figure 13. Third-Order Intermodulation Distortion at 10.7 MHz (10× Probe Used to HP3585A Spectrum Analyzer, Gain = 0 dB, PIN = 0 dBm) Figure 10. Histogram of VOS at 10 dB Gain and VOS vs. VGAIN –1.0 553 PIECE SAMPLE SIZE –1.2 –1.4 40 NEGATIVE OUTPUT VOLTAGE (V) PERCENTAGE OF SAMPLES (%) 50 00539-012 10 00539-057 PERCENTAGE OF SAMPLES (%) 60 AD603 GPOS GNEG 30 20 10 –1.6 –1.8 –2.0 –2.2 –2.4 –2.6 –2.8 –3.0 85 90 95 100 105 110 –3.4 00539-058 0 115 PIN GPOS AND PIN GNEG BIAS CURRENT (nA) 0 50 100 200 500 1000 LOAD RESISTANCE (Ω) 00539-013 –3.2 2000 Figure 14. Typical Output Voltage Swing vs. Load Resistance (Negative Output Swing Limits First) Figure 11. Histogram of GPOS and GNEG Bias Current 102 INPUT IMPEDANCE (Ω) 10dB/DIV 100 98 96 00539-011 100k Figure 12. Third-Order Intermodulation Distortion at 455 kHz (10× Probe Used to HP3585A Spectrum Analyzer, Gain = 0 dB, PIN = 0 dBm) Rev. K | Page 7 of 24 1M 10M FREQUENCY (Hz) 100M Figure 15. Input Impedance vs. Frequency (Gain = −10 dB) 00539-014 94 AD603 Data Sheet 4.5V 102 INPUT IMPEDANCE (Ω) INPUT GND 1V/DIV 100 98 500mV 96 OUTPUT GND 500mV/DIV 1M 10M FREQUENCY (Hz) 100M –500mV –49ns 451ns Figure 19. Input Stage Overload Recovery Time (Input Is 500 ns Period, 50% Duty-Cycle Square Wave, Output Is Captured Using Tektronix 11402 Digitizing Oscilloscope) Figure 16. Input Impedance vs. Frequency (Gain = 10 dB) 102 3V 100 INPUT GND 100MV/DIV 98 1V OUTPUT GND 1V/DIV 96 1M 10M FREQUENCY (Hz) 100M Figure 17. Input Impedance vs. Frequency (Gain = 30 dB) –2V –49ns 50ns 451ns 00539-019 100k 00539-016 94 Figure 20. Output Stage Overload Recovery Time (Input Is 500 ns Period, 50% Duty-Cycle Square Wave, Output Is Captured Using Tektronix 11402 Digitizing Oscilloscope) 3.5V 1V INPUT 500mV/DIV 100 90 GND 500mV OUTPUT 500mV/DIV GND 1V 200ns –1.5V –44ns 50ns 456ns Figure 18. Gain Control Channel Response Time Figure 21. Transient Response, G = 0 dB (Input Is 500 ns Period, 50% Duty-Cycle Square Wave, Output Is Captured Using Tektronix 11402 Digitizing Oscilloscope) Rev. K | Page 8 of 24 00539-020 10 0% 00539-017 INPUT IMPEDANCE (Ω) 50ns 00539-018 100k 00539-015 94 Data Sheet AD603 21 3.5V TA = 25°C RS = 50Ω TEST SETUP FIGURE 23 10MHz 19 17 NOISE FIGURE (dB) INPUT GND 100mV/DIV 500mV OUTPUT GND 500mV/DIV 15 20MHz 13 11 9 50ns 456ns 5 30 00539-021 –1.5V –44ns Figure 22. Transient Response, G = 20 dB (Input Is 500 ns Period, 50% Duty-Cycle Square Wave, Output Is Captured Using Tektronix 11402 Digitizing Oscilloscope) 31 32 33 34 35 36 GAIN (dB) 37 38 39 40 00539-025 7 Figure 25. Noise Figure in 0 dB/40 dB Mode 0 TA = 25°C TEST SETUP FIGURE 23 0 –5 INPUT LEVEL (dBm) –10 PSRR (dB) –20 –30 –40 –50 –10 –15 –60 1M 10M FREQUENCY (Hz) 100M Figure 23. PSRR vs. Frequency (Worst Case Is Negative Supply PSRR, Shown Here) –25 10 30 50 INPUT FREQUENCY (MHz) Figure 26. 1 dB Compression Point, −10 dB/+30 dB Mode, Gain = 30 dB 20 23 21 TA = 25°C RS = 50V TEST SETUP FIGURE 23 70MHz 70 00539-026 100k 00539-022 –20 TA = 25°C TEST SETUP FIGURE 23 18 30MHz OUTPUT LEVEL (dBm) 17 50MHz 15 13 30MHz 11 10MHz 9 16 40MHz 14 12 70MHz 10 5 20 21 22 23 24 25 26 GAIN (dB) 27 28 29 30 0 –20 –10 INPUT LEVEL (dBm) 0 00539-027 7 00539-024 NOISE FIGURE (dB) 19 Figure 27. Third-Order Intercept −10 dB/+30 dB Mode, Gain = 10 dB Figure 24. Noise Figure in −10 dB/+30 dB Mode Rev. K | Page 9 of 24 AD603 Data Sheet 20 18 16 40MHz 14 12 70MHz 10 8 –40 –30 INPUT LEVEL (dBm) –20 00539-028 OUTPUT LEVEL (dBm) 30MHz TA = 25°C RS = 50Ω RIN = 50Ω RL = 100Ω TEST SETUP FIGURE 23 Figure 28. Third-Order Intercept −10 dB/+30 dB Mode, Gain = 30 dB Rev. K | Page 10 of 24 Data Sheet AD603 TEST CIRCUITS 0.1µF +5V HP3326A DUALCHANNEL SYNTHESIZER 8 3 5 AD603 100Ω 10× PROBE 7 2 4 1 HP3585A SPECTRUM ANALYZER 511Ω 6 0.1µF 00539-010 –5V DATEL DVC 8500 Figure 29. Third-Order Intermodulation Distortion Test Setup 0.1µF +5V HP3326A DUALCHANNEL SYNTHESIZER 8 3 50Ω 5 AD603 100Ω 7 2 4 HP3585A SPECTRUM ANALYZER 1 6 –5V DATEL DVC 8500 00539-023 0.1µF Figure 30. Test Setup Used for: Noise Figure, Third-Order Intercept, and 1 dB Compression Point Measurements Rev. K | Page 11 of 24 AD603 Data Sheet THEORY OF OPERATION The AD603 comprises a fixed-gain amplifier, preceded by a broadband passive attenuator of 0 dB to 42.14 dB, having a gain control scaling factor of 40 dB per volt. The fixed gain is lasertrimmed in two ranges, to either 31.07 dB (×35.8) or 50 dB (×358), or it may be set to any range in between using one external resistor between Pin 5 and Pin 7. Somewhat higher gain can be obtained by connecting the resistor from Pin 5 to common, but the increase in output offset voltage limits the maximum gain to about 60 dB. For any given range, the bandwidth is independent of the voltage-controlled gain. This system provides an underrange and overrange of 1.07 dB in all cases; for example, the overall gain is −11.07 dB to +31.07 dB in the maximum bandwidth mode (Pin 5 and Pin 7 strapped). This X-AMP structure has many advantages over former methods of gain control based on nonlinear elements. Most importantly, the fixed-gain amplifier can use negative feedback to increase its accuracy. Because large inputs are first attenuated, the amplifier input is always small. For example, to deliver a ±1 V output in the −1 dB/+41 dB mode (that is, using a fixed amplifier gain of 41.07 dB), its input is only 8.84 mV; therefore, the distortion can be very low. Equally important, the smallsignal gain and phase response, and thus the pulse response, are essentially independent of gain. Figure 31 is a simplified schematic. The input attenuator is a 7-section R-2R ladder network, using untrimmed resistors of nominally R = 62.5 Ω, which results in a characteristic resistance of 125 Ω ± 20%. A shunt resistor is included at the input and laser trimmed to establish a more exact input resistance of 100 Ω ± 3%, which ensures accurate operation (gain and HP corner frequency) when used in conjunction with external resistors or capacitors. The nominal maximum signal at input VINP is 1 V rms (±1.4 V peak) when using the recommended ±5 V supplies, although operation to ±2 V peak is permissible with some increase in HF distortion and feedthrough. Pin 4 (COMM) must be connected directly to the input ground; significant impedance in this connection reduces the gain accuracy. The signal applied at the input of the ladder network is attenuated by 6.02 dB by each section; therefore, the attenuation to each of the taps is progressively 0 dB, 6.02 dB, 12.04 dB, 18.06 dB, 24.08 dB, 30.1 dB, 36.12 dB, and 42.14 dB. A unique circuit technique is employed to interpolate between these tap points, indicated by the slider in Figure 31, thus providing continuous attenuation from 0 dB to 42.14 dB. It helps in understanding the AD603 to think in terms of a mechanical means for moving this slider from left to right; in fact, its position is controlled by the voltage between Pin 1 and Pin 2. The details of the gain control interface are in the The Gain Control Interface section. The gain is at all times very exactly determined, and a linear-indB relationship is automatically guaranteed by the exponential nature of the attenuation in the ladder network (the X-AMP principle). In practice, the gain deviates slightly from the ideal law, by about ±0.2 dB peak (see, for example, Figure 5). NOISE PERFORMANCE An important advantage of the X-AMP is its superior noise performance. The nominal resistance seen at inner tap points is 41.7 Ω (one third of 125 Ω), which exhibits a Johnson noise spectral density (NSD) of 0.83 nV/√Hz (that is, √4kTR) at 27°C, which is a large fraction of the total input noise. The first stage of the amplifier contributes a further 1 nV/√Hz, for a total input noise of 1.3 nV/√Hz. It is apparent that it is essential to use a low resistance in the ladder network to achieve the very low specified noise level. The source impedance of the signal forms a voltage divider with the 100 Ω input resistance of the AD603. In some applications, the resulting attenuation may be unacceptable, requiring the use of an external buffer or preamplifier to match a high impedance source to the low impedance AD603. The noise at maximum gain (that is, at the 0 dB tap) depends on whether the input is short-circuited or open-circuited. When short-circuited, the minimum NSD of slightly over 1 nV/√Hz is achieved. When open-circuited, the resistance of 100 Ω looking into the first tap generates 1.29 nV/√Hz, so the noise increases to 1.63 nV/√Hz. (This last calculation would be important if the AD603 were preceded by, for example, a 900 Ω resistor to allow operation from inputs up to 10 V rms.) As the selected tap moves away from the input, the dependence of the noise on source impedance quickly diminishes. Apart from the small variations just discussed, the signal-tonoise (SNR) at the output is essentially independent of the attenuator setting. For example, on the −11 dB/+31 dB range, the fixed gain of ×35.8 raises the output NSD to 46.5 nV/√Hz. Therefore, for the maximum undistorted output of 1 V rms and a 1 MHz bandwidth, the output SNR would be 86.6 dB, that is, 20 log(1 V/46.5 µV). Rev. K | Page 12 of 24 Data Sheet AD603 VPOS 8 SCALING REFERENCE VNEG 6 PRECISION PASSIVE INPUT ATTENUATOR FIXED-GAIN AMPLIFIER GPOS 1 7 VOUT 5 FDBK VG GNEG 2 6.44kΩ* AD603 GAINCONTROL INTERFACE 694Ω* 0dB VINP 3 –6.02dB R 2R –12.04dB –18.06dB –24.08dB R 2R R 2R R 2R –30.1dB R 2R –36.12dB –42.14dB R 2R R 20Ω* R COMM 4 00539-029 R-2R LADDER NETWORK *NOMINAL VALUES. Figure 31. Simplified Block Diagram THE GAIN CONTROL INTERFACE The attenuation is controlled through a differential, high impedance (50 MΩ) input, with a scaling factor that is lasertrimmed to 40 dB per volt, that is, 25 mV/dB. An internal band gap reference ensures stability of the scaling with respect to supply and temperature variations. When the differential input voltage VG = 0 V, the attenuator slider is centered, providing an attenuation of 21.07 dB. For the maximum bandwidth range, this results in an overall gain of 10 dB (= −21.07 dB + 31.07 dB). When the control input is −500 mV, the gain is lowered by +20 dB (= 0.500 V × 40 dB/V) to −10 dB; when set to +500 mV, the gain is increased by +20 dB to +30 dB. When this interface is overdriven in either direction, the gain approaches either −11.07 dB (= − 42.14 dB + +31.07 dB) or 31.07 dB (= 0 + 31.07 dB), respectively. The only constraint on the gain control voltage is that it be kept within the common-mode range (−1.2 V to +2.0 V assuming +5 V supplies) of the gain control interface. The basic gain of the AD603 can therefore be calculated by Gain (dB) = 40 VG +10 (1) where VG is in volts. When Pin 5 and Pin 7 are strapped (see the Programming the Fixed-Gain Amplifier Using Pin Strapping section), the gain becomes For example, if the gain is to be controlled by a DAC providing a positive-only, ground-referenced output, the gain control low (GNEG) pin should be biased to a fixed offset of 500 mV to set the gain to −10 dB when gain control high (GPOS) is at zero, and to 30 dB when at 1.00 V. It is a simple matter to include a voltage divider to achieve other scaling factors. When using an 8-bit DAC having an FS output of 2.55 V (10 mV/bit), a divider ratio of 2 (generating 5 mV/bit) results in a gain-setting resolution of 0.2 dB/bit. The use of such offsets is valuable when two AD603s are cascaded, when various options exist for optimizing the signal-to-noise profile, as is shown in the Sequential Mode (Optimal SNR) section, PROGRAMMING THE FIXED-GAIN AMPLIFIER USING PIN STRAPPING Access to the feedback network is provided at Pin 5 (FDBK). The user may program the gain of the output amplifier of the AD603 using this pin, as shown in Figure 32, Figure 33, and Figure 34. There are three modes: in the default mode, FDBK is unconnected, providing the range +9 dB/+51 dB; when VOUT and FDBK are shorted, the gain is lowered to −11 dB/+31 dB; and, when an external resistor is placed between VOUT and FDBK, any intermediate gain can be achieved, for example, −1 dB/+41 dB. Figure 35 shows the nominal maximum gain vs. external resistor for this mode. Gain (dB) = 40 VG + 20 for 0 to +40 dB VC1 and 1 GPOS VPOS 8 VPOS AD603 VC2 (2) The high impedance gain control input ensures minimal loading when driving many amplifiers in multiple channel or cascaded applications. The differential capability provides flexibility in choosing the appropriate signal levels and polarities for various control schemes. Rev. K | Page 13 of 24 VIN 2 GNEG VOUT 7 3 VINP VNEG 6 4 COMM FDBK 5 VOUT VNEG Figure 32. −10 dB to +30 dB; 90 MHz Bandwidth 00539-030 Gain (dB) = 40 VG + 30 for +10 to +50 dB AD603 Data Sheet VC1 1 GPOS VC2 2 GNEG VOUT 7 3 VINP VNEG 6 4 COMM FDBK 5 VPOS 8 Optionally, when a resistor is placed from FDBK to COMM, higher gains can be achieved. This fourth mode is of limited value because of the low bandwidth and the elevated output offsets; it is thus not included in Figure 32, Figure 33, or Figure 34. VPOS AD603 VIN VOUT VNEG 2.15kΩ The gain of this amplifier in the first two modes is set by the ratio of on-chip laser-trimmed resistors. While the ratio of these resistors is very accurate, the absolute value of these resistors can vary by as much as ±20%. Therefore, when an external resistor is connected in parallel with the nominal 6.44 kΩ ± 20% internal resistor, the overall gain accuracy is somewhat poorer. The worst-case error occurs at about 2 kΩ (see Figure 36). 00539-031 5.6pF Figure 33. 0 dB to 40 dB; 30 MHz Bandwidth VC1 1 GPOS VPOS 8 VPOS AD603 VC2 2 GNEG VOUT 7 3 VINP VNEG 6 4 COMM FDBK 5 VOUT 1.2 VNEG 0.8 0.6 GAIN ERROR (dB) 18pF Figure 34. 10 dB to 50 dB; 9 MHz to Set Gain 52 50 –1:VdB (OUT) 48 0.4 0.2 0 –0.2 –0.4 46 –0.6 –1.0 10 –2:VdB (OUT) 40 VdB (OUT) – VdB (OREF ) 100 1k 10k REXT (Ω) 38 100k 1M 00539-034 –0.8 VdB (OUT) 42 Figure 36. Worst-Case Gain Error, Assuming Internal Resistors Have a Maximum Tolerance of −20% (Top Curve) or = 20% (Bottom Curve) 36 34 32 100 1k 10k REXT (Ω) 100k 1M 00539-033 GAIN (dB) 44 30 10 –1:VdB (OUT) – (–1):VdB (OREF ) 1.0 00539-032 VIN Figure 35. Gain vs. REXT, Showing Worst-Case Limits Assuming Internal Resistors Have a Maximum Tolerance of 20% While the gain bandwidth product of the fixed-gain amplifier is about 4 GHz, the actual bandwidth is not exactly related to the maximum gain. This is because there is a slight enhancing of the ac response magnitude on the maximum bandwidth range, due to higher order poles in the open-loop gain function; this mild peaking is not present on the higher gain ranges. Figure 32, Figure 33, and Figure 34 show how an optional capacitor may be added to extend the frequency response in high gain modes. Rev. K | Page 14 of 24 Data Sheet AD603 USING THE AD603 IN CASCADE Figure 37 shows the SNR over a gain range of −22 dB to +62 dB, assuming an output of 1 V rms and a 1 MHz bandwidth. Figure 38, Figure 39, and Figure 40 show the general connections to accomplish this. Here, both the positive gain control inputs (GPOS) are driven in parallel by a positive-only, ground-referenced source with a range of 0 V to 2 V, while the negative gain control inputs (GNEG) are biased by stable voltages to provide the needed gain offsets. These voltages may be provided by resistive dividers operating from a common voltage reference. Two or more AD603s can be connected in series to achieve higher gain. Invariably, ac coupling must be used to prevent the dc offset voltage at the output of each amplifier from overloading the following amplifier at maximum gain. The required highpass coupling network is usually just a capacitor, chosen to set the desired corner frequency in conjunction with the welldefined 100 Ω input resistance of the following amplifier. For two AD603s, the total gain control range becomes 84 dB (2 × 42.14 dB); the overall −3 dB bandwidth of cascaded stages is somewhat reduced. Depending on the pin strapping, the gain and bandwidth for two cascaded amplifiers can range from −22 dB to +62 dB (with a bandwidth of about 70 MHz) to +22 dB to +102 dB (with a bandwidth of about 6 MHz). 90 85 80 75 SNR (dB) There are several ways of connecting the gain control inputs in cascaded operation. The choice depends on whether it is important to achieve the highest possible instantaneous signalto-noise ratio (ISNR), or, alternatively, to minimize the ripple in the gain error. The following examples feature the AD603 programmed for maximum bandwidth; the explanations apply to other gain/bandwidth combinations with appropriate changes to the arrangements for setting the maximum gain. 70 65 60 50 –0.2 SEQUENTIAL MODE (OPTIMAL SNR) A1 GNEG VG1 –51.07dB 31.07dB –8.93dB –42.14dB GPOS VG2 VO1 = 0.473V VC = 0V GNEG 31.07dB OUTPUT –20dB VO2 = 1.526V 00539-036 –42.14dB 1.0 VC (V) A2 –40.00dB GPOS 0.6 Figure 38. AD603 Gain Control Input Calculations for Sequential Control Operation VC = 0 V –11.07dB 0dB GPOS GNEG VG1 31.07dB 31.07dB –42.14dB GPOS VG2 VO1 = 0.473V VC = 1.0V GNEG 31.07dB OUTPUT 20dB VO2 = 1.526V 00539-037 0dB INPUT 0dB Figure 39. AD603 Gain Control Calculations for Sequential Control Operation VC = 1.0 V 0dB GPOS GNEG VG1 VC = 2.0V –28.93dB 31.07dB VO1 = 0.473V 31.07dB –2.14dB GPOS GNEG VG2 31.07dB OUTPUT 60dB VO2 = 1.526V Figure 40. AD603 Gain Control Input Calculations for Sequential Operation VC = 2.0 V Rev. K | Page 15 of 24 00539-038 0dB INPUT 0dB 1.4 1.8 2.2 Figure 37. SNR vs. Control Voltage, Sequential Control (1 MHz Bandwidth) In the sequential mode of operation, the ISNR is maintained at its highest level for as much of the gain control range as possible. INPUT 0dB 0.2 00539-035 55 AD603 Data Sheet Gain (dB) = 40 VG + GO (3) Figure 43 is a plot of the SNR of the cascaded amplifiers vs. the control voltage. Figure 44 is a plot of the gain error of the cascaded stages vs. the control voltages. 70 60 20 10 0 A2 0.2 0.6 1.0 VC (V) 1.4 1.8 2.0 00539-040 –30 –0.2 Figure 42. Plot of Separate and Overall Gains in Sequential Control 90 +31.07dB 80 +31.07dB +28.96dB 70 A2 * –11.07dB * 60 SNR (dB) A1 –8.93dB –11.07dB 1.526 0.5 0 1.0 20 1.50 40 2.0 60 VC (V) 62.14 *GAIN OFFSET OF 1.07dB, OR 26.75mV. 00539-039 0.473 0 –20 A1 30 –20 In the explanatory notes that follow, it is assumed that the maximum bandwidth connections are used, for which GO is −20 dB. GAIN (dB) –22.14 40 –10 where: VG is the applied control voltage. GO is determined by the gain range chosen. +10dB COMBINED 50 OVERALL GAIN (dB) The gains are offset (Figure 41) such that the gain of A2 is increased only after the gain of A1 has reached its maximum value. Note that for a differential input of –600 mV or less, the gain of a single amplifier (A1 or A2) is at its minimum value of −11.07 dB; for a differential input of 600 mV or more, the gain is at its maximum value of 31.07 dB. Control inputs beyond these limits do not affect the gain and can be tolerated without damage or foldover in the response. This is an important aspect of the gain control response of the AD603. (See the Specifications section for more details on the allowable voltage range.) The gain is now 50 40 30 20 When VG = 2.0 V, the gain of A1 is pinned at 31.07 dB and that of A2 is near its maximum value of 28.93 dB, resulting in an overall gain of 60 dB (see Figure 40). This mode of operation is further clarified in Figure 42, which is a plot of the separate gains of A1 and A2 and the overall gain vs. the control voltage. 0.2 0.6 1.0 VC (V) 1.4 1.8 2.0 Figure 43. SNR for Cascaded Stages—Sequential Control 2.0 1.5 1.0 0.5 0 –0.5 –1.0 –1.5 –2.0 –0.2 0 0.2 0.4 0.6 0.8 1.0 1.2 VC (V) 1.4 1.6 1.8 2.0 2.2 Figure 44. Gain Error for Cascaded Stages–Sequential Control PARALLEL MODE (SIMPLEST GAIN CONTROL INTERFACE) In this mode, the gain control of voltage is applied to both inputs in parallel: the GPOS pins of both A1 and A2 are Rev. K | Page 16 of 24 00539-042 When VG = 1.00 V, VG1 = 1.00 V − 0.473 V = 0.526 V, which sets the gain of A1 to nearly its maximum value of +31.07 dB, while VG2 = 1.00 V − 1.526 V = 0.526 V, which sets the gain of A2 to nearly its minimum value of −11.07 dB. Close analysis shows that the degree to which neither AD603 is completely pushed to its maximum nor minimum gain exactly cancels in the overall gain, which is now 20 dB (see Figure 39). 10 –0.2 GAIN ERROR (dB) With reference to Figure 38, Figure 39, and Figure 40, note that VG1 refers to the differential gain control input to A1, and VG2 refers to the differential gain control input to A2. When VG is 0 V, VG1 = −473 mV and thus the gain of A1 is −8.93 dB (recall that the gain of each individual amplifier in the maximum bandwidth mode is –10 dB for VG = −500 mV and 10 dB for VG = 0 V); meanwhile, VG2 = −1.908 V so the gain of A2 is pinned at −11.07 dB. The overall gain is therefore –20 dB (see Figure 38). 00539-041 Figure 41. Explanation of Offset Calibration for Sequential Control Data Sheet AD603 LOW GAIN RIPPLE MODE (MINIMUM GAIN ERROR) connected to the control voltage and the GNEW inputs are grounded. The gain scaling is then doubled to 80 dB/V, requiring only a 1.00 V change for an 80 dB change of gain Gain = (dB) = 80 VG + GO (4) where, as before, GO depends on the range selected; for example, in the maximum bandwidth mode, GO is 20 dB. Alternatively, the GNEG pins may be connected to an offset voltage of 0.500 V, in which case GO is −20 dB. The amplitude of the gain ripple in this case is also doubled, as shown in Figure 45, while the ISNR at the output of A2 now decreases linearly as the gain increases, as shown in Figure 46. As can be seen in Figure 44 and Figure 45, the error in the gain is periodic, that is, it shows a small ripple. (Note that there is also a variation in the output offset voltage, which is due to the gain interpolation, but this is not exact in amplitude.) By offsetting the gains of A1 and A2 by half the period of the ripple, that is, by 3 dB, the residual gain errors of the two amplifiers can be made to cancel. Figure 47 shows much lower gain ripple when configured in this manner. Figure 48 plots the ISNR as a function of gain; it is very similar to that in the parallel mode. 3.0 2.5 2.0 2.0 1.5 GAIN ERROR (dB) 1.5 0.5 0 0.5 0 –0.5 –1.0 –1.5 –0.5 –2.0 –1.0 –3.0 –0.1 0 0.2 0.4 0.6 0.8 1.0 1.2 VC (V) 1.4 1.6 1.8 2.0 2.2 00539-043 –2.0 –0.2 85 80 80 75 ISNR (dB) 85 75 70 60 55 55 50 –0.2 0.8 1.0 1.2 0.5 0.6 VC (V) 0.7 0.8 0.9 1.0 1.1 0 0.2 0.4 0.6 0.8 1.0 1.2 VC (V) 00539-044 0.6 VC (V) 0.4 65 60 0.4 0.3 70 65 0.2 0.2 Figure 47. Gain Error for Cascaded Stages—Low Ripple Mode Figure 45. Gain Error for Cascaded Stages—Parallel Control 0 0.1 90 90 50 –0.2 0 00539-045 –2.5 –1.5 ISNR (dB) 1.0 Figure 48. ISNR vs. Control Voltage—Low Ripple Mode Figure 46. ISNR for Cascaded Stages—Parallel Control Rev. K | Page 17 of 24 00539-046 GAIN ERROR (dB) 1.0 AD603 Data Sheet APPLICATIONS INFORMATION A LOW NOISE AGC AMPLIFIER The circuit operates as follows: Figure 49 shows the ease with which the AD603 can be connected as an AGC amplifier. The circuit illustrates many of the points previously discussed: it uses few parts, has linear-indB gain, operates from a single supply, uses two cascaded amplifiers in sequential gain mode for maximum SNR, and an external resistor programs each gain of the amplifier. It also uses a simple temperature-compensated detector. A1 and A2 are cascaded. Capacitor C1 and the 100 Ω of resistance at the input of A1 form a time constant of 10 μs. C2 blocks the small dc offset voltage at the output of A1 (which might otherwise saturate A2 at its maximum gain) and introduces a high-pass corner at about 16 kHz, eliminating low frequency noise. The circuit operates from a single 10 V supply. Resistors R1, R2, R3, and R4 bias the common pins of A1 and A2 at 5 V. The common pin is a low impedance point and must have a low impedance path to ground, provided here by the 100 μF tantalum capacitors and the 0.1 μF ceramic capacitors. A half-wave detector is used, based on Q1 and R8. The current into capacitor, CAV, is the difference between the collector current of Q2 (biased to be 300 μA at 300 K, 27°C) and the collector current of Q1, which increases with the amplitude of the output signal. The cascaded amplifiers operate in sequential gain. Here, the offset voltage between Pin 2 (GNEG) of A1 and A2 is 1.05 V (42.14 dB × 25 mV/dB), provided by a voltage divider consisting of Resistors R5, R6, and R7. Using standard values, the offset is not exact, but it is not critical for this application. The automatic gain control voltage, VAGC, is the time integral of this error current. For VAGC (and thus the gain) to remain insensitive to short-term amplitude fluctuations in the output signal, the rectified current in Q1 must, on average, exactly balance the current in Q2. If the output of A2 is too small to do this, VAGC increases, causing the gain to increase until Q1 conducts sufficiently. The gain of both A1 and A2 is programmed by Resistors R13 and R14, respectively, to be about 42 dB; therefore, the maximum gain of the circuit is twice that, or 84 dB. The gain control range can be shifted up by as much as 20 dB by appropriate choices of R13 and R14. Consider the case where R8 is zero and the output voltage VOUT is a square wave at, for example, 455 kHz, which is well above the corner frequency of the control loop. 10V C7 0.1µF 10V C1 0.1µF J1 R1 2.49kΩ + C4 0.1µF 5 8 7 A2 AD603 10V 1 C 52 100µF + C6 0.1µF Q1 2N3904 R8 806Ω 5 R11 3.83kΩ 5V R1 2 4.99kΩ C9 0.1µF J2 7 2 C10 0.1µF 4 R3 2.49kΩ R2 2.49kΩ CAV 0.1µF 6 3 2 4 R1 4 2.49kΩ C11 0.1µF 1 R4 2.49kΩ AGC LINE 1V OFFSET FOR SEQUENTIAL GAIN R5 5.49kΩ 5.5V R6 1.05kΩ R7 3.48kΩ 6.5V 10V 00539-047 C 32 100µF C2 0.1µF 6 A1 AD603 10V 10V R1 0 1.24kΩ Q2 2N3906 VAGC C8 0.1µF R1 3 2.49kΩ 8 3 R T1 100Ω R9 1.54kΩ THIS CAPACITOR SETS AGC TIME CONSTANT 1 RT PR OVI D ES A 5 0Ω IN PU T I MPED A N C E. 2 C 3 A N D C 5 A R E TA NTA LU M. Figure 49. A Low Noise AGC Amplifier Rev. K | Page 18 of 24 Data Sheet AD603 During the time VOUT is negative with respect to the base voltage of Q1, Q1 conducts; when VOUT is positive, it is cut off. Because the average collector current of Q1 is forced to be 300 µA, and the square wave has a duty cycle of 1:1, Q1’s collector current when conducting must be 600 µA. With R8 omitted, the peak amplitude of VOUT is forced to be just the VBE of Q1 at 600 µA, typically about 700 mV, or 2 VBE peak-to-peak. This voltage, the amplitude at which the output stabilizes, has a strong negative temperature coefficient (TC), typically −1.7 mV/°C. Although this may not be troublesome in some applications, the correct value of R8 renders the output stable with temperature. To understand this, note that the current in Q2 is made to be proportional to absolute temperature (PTAT). For the moment, continue to assume that the signal is a square wave. When Q1 is conducting, VOUT is now the sum of VBE and a voltage that is PTAT and that can be chosen to have an equal but opposite TC to that of the VBE. This is actually nothing more than an application of the band gap voltage reference principle. When R8 is chosen such that the sum of the voltage across it and the VBE of Q1 is close to the band gap voltage of about 1.2 V, VOUT is stable over a wide range of temperatures, provided, of course, that Q1 and Q2 share the same thermal environment. Because the average emitter current is 600 µA during each half cycle of the square wave, a resistor of 833 Ω adds a PTAT voltage of 500 mV at 300 K, increasing by 1.66 mV/°C. In practice, the optimum value depends on the type of transistor used and, to a lesser extent, on the waveform for which the temperature stability is to be optimized; for the inexpensive 2N3904/2N3906 pair and sine wave signals, the recommended value is 806 Ω. This resistor also serves to lower the peak current in Q1 when more typical signals (usually sinusoidal) are involved, and the 1.8 kHz LP filter it forms with CAV helps to minimize distortion due to ripple in VAGC. Note that the output amplitude under sine wave conditions is higher than for a square wave because the average value of the current for an ideal rectifier is 0.637 times as large, causing the output amplitude to be 1.88 (= 1.2/0.637) V, or 1.33 V rms. In practice, the somewhat nonideal rectifier results in the sine-wave output being regulated to about 1.4 V rms, or 3.6 V p-p. The bandwidth of the circuit exceeds 40 MHz. At 10.7 MHz, the AGC threshold is 100 µV (−67 dBm) and its maximum gain is 83 dB (20 log 1.4 V/100 µV). The circuit holds its output at 1.4 V rms for inputs as low as −67 dBm to +15 dBm (82 dB), where the input signal exceeds the maximum input rating of the AD603. For a 30 dBm input at 10.7 MHz, the second harmonic is 34 dB down from the fundamental, and the third harmonic is 35 dB down from the fundamental. CAUTION Careful component selection, circuit layout, power supply decoupling, and shielding are needed to minimize the susceptibility of the AD603 to interference from signals such as those from radio and TV stations. In bench evaluation, it is recommended to place all of the components into a shielded box and use feedthrough decoupling networks for the supply voltage. Circuit layout and construction are also critical because stray capacitances and lead inductances can form resonant circuits and are a potential source of circuit peaking, oscillation, or both. Rev. K | Page 19 of 24 AD603 Data Sheet EVALUATION BOARD The output is also ac-coupled and includes a 453 Ω series resistor. Set the AD603 gain by connecting a voltage source between the GNEG and GPOS test loops. The two slide switches SGPOS and SGNEG provide three connections for GPOS and the GNEG. Either pin can be ground referenced, or biased with a user selected voltage established by R1 and R5 to R7. A signal generator can be connected to the GPOS or GNEG test loops, or the GNEG can be driven to either polarity within the common-mode limits of −1.2 V to +2.0 V; to invert the gain slope, simply reverse the polarity of the voltage source connected to GPOS and GNEG. For bias current measurements, the third switch option disconnects the bias voltage source and permits connection of a microammeter between the GPOS and GNEG pins to ground. 00539-049 The evaluation board of the AD603 enables simple bench-top experimenting to be performed with easy control of the AD603. Built-in flexibility allows convenient configuration to accommodate most operating configurations. Figure 50 is a photograph of the AD603 evaluation board. Figure 50. AD603 Evaluation Board Any dual-polarity power supply capable of providing 20 mA is all that is required, in addition to whatever test equipment the user wishes to perform the intended tests. The AD603 includes built-in gain resistors selectable at the FDBK pin. The board is shipped with the gain at minimum, with a 0 Ω resistor installed in R3. For maximum gain, simply remove R3. Because of the architecture of the AD603, the bandwidth decreases by 10, but the gain range remains at 40 dB. Intermediate gain values may be selected by installing a resistor between the VOUT and FDBK pins. Figure 52, Figure 53, and Figure 56 show the component and circuit side copper patterns and silkscreen. Referring to the schematic in Figure 51, the input to the VGA is single-ended, ac-coupled, and terminated in 50 Ω to accommodate most commonly available signal generators. G1 VPOS GND VNEG C7 C8 10µF 10µF 25V 25V G3 G4 G5 G6 + + VPOS VPOS VNEG VPOS GPOS GPOSS R7 G2 C1 0.1µF SGPOS 00539-051 C2 0.1µF R1 VO VNEG VPOS GNEGS R6 AD603 GNEG C4 SGNEG 0.1µF 1 C5 0.1µF VNEG 3 4 VIN W2 R2 100Ω R4 453Ω VOUT 8 GPOS VPOS 2 R5 C6 0.1µF GNEG VOUT VINP VNEG COMM FDBK W1 7 6 5 C9 R3 0Ω VNEG C3 0.1µF VPOS R8 SCOM 00539-050 R9 VNEG Figure 51. Schematic of the AD603 Evaluation Board Rev. K | Page 20 of 24 Figure 52. Component Side Copper AD603 Figure 53. Secondary Side Copper 00539-054 00539-052 Data Sheet 00539-055 00539-053 Figure 55. Inner Layer Power Plane Figure 56. Component Side Silk Screen Figure 54. Inner Layer Ground Plane Rev. K | Page 21 of 24 AD603 Data Sheet OUTLINE DIMENSIONS 0.005 (0.13) MIN 0.055 (1.40) MAX 8 5 0.310 (7.87) 0.220 (5.59) 1 4 0.100 (2.54) BSC 0.320 (8.13) 0.290 (7.37) 0.405 (10.29) MAX 0.060 (1.52) 0.015 (0.38) 0.200 (5.08) MAX 0.150 (3.81) MIN 0.200 (5.08) 0.125 (3.18) 0.023 (0.58) 0.014 (0.36) 0.070 (1.78) 0.030 (0.76) SEATING PLANE 15° 0° 0.015 (0.38) 0.008 (0.20) CONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETER DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF INCH EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN. Figure 57. 8-Lead Ceramic Dual In-Line Package [CERDIP] (Q-8) Dimensions shown in inches and (millimeters) 5.00 (0.1968) 4.80 (0.1890) 1 5 6.20 (0.2441) 5.80 (0.2284) 4 1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0040) COPLANARITY 0.10 SEATING PLANE 1.75 (0.0688) 1.35 (0.0532) 0.51 (0.0201) 0.31 (0.0122) 0.50 (0.0196) 0.25 (0.0099) 45° 8° 0° 0.25 (0.0098) 0.17 (0.0067) 1.27 (0.0500) 0.40 (0.0157) COMPLIANT TO JEDEC STANDARDS MS-012-AA CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN. Figure 58. 8-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-8) Dimensions shown in millimeters and (inches) Rev. K | Page 22 of 24 012407-A 8 4.00 (0.1574) 3.80 (0.1497) Data Sheet AD603 0.07 12-07-2011-A 0.088 TOP VIEW (CIRCUIT SIDE) Figure 59. 9-Pad Bare Die [CHIP] (C-9-1) Dimensions Shown in Inches ORDERING GUIDE Model 1, 2 AD603AR AD603AR-REEL AD603AR-REEL7 AD603ARZ AD603ARZ-REEL AD603ARZ-REEL7 AD603AQ AD603SQ/883B AD603-EVALZ AD603ACHIPS 1 2 Temperature Range −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −55°C to +125°C Package Description 8-Lead SOIC_N 8-Lead SOIC_N, 13" Tape and Reel 8-Lead SOIC_N, 7" Tape and Reel 8-Lead SOIC_N 8-Lead SOIC_N, 13" Tape and Reel 8-Lead SOIC_N, 7" Tape and Reel 8-Lead CERDIP 8-Lead CERDIP Evaluation Board DIE Z = RoHS Compliant Part. For AD603SQ/883B, refer to AD603 Military data sheet. Also available as 5962-9457203MPA. Rev. K | Page 23 of 24 Package Option R-8 R-8 R-8 R-8 R-8 R-8 Q-8 Q-8 C-9-1 AD603 Data Sheet NOTES ©1993–2012 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D00539-0-4/12(K) Rev. K | Page 24 of 24