LT1206 250mA/60MHz Current Feedback Amplifier FEATURES DESCRIPTION ■ The LT®1206 is a current feedback amplifier with high output current drive capability and excellent video characteristics. The LT1206 is stable with large capacitive loads, and can easily supply the large currents required by the capacitive loading. A shutdown feature switches the device into a high impedance, low current mode, reducing dissipation when the device is not in use. For lower bandwidth applications, the supply current can be reduced with a single external resistor. The low differential gain and phase, wide bandwidth, and the 250mA minimum output current drive make the LT1206 well suited to drive multiple cables in video systems. ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ 250mA Minimum Output Drive Current 60MHz Bandwidth, AV = 2, RL = 100Ω 900V/µs Slew Rate, AV = 2, RL = 50Ω 0.02% Differential Gain, AV = 2, RL = 30Ω 0.17° Differential Phase, AV = 2, RL = 30Ω High Input Impedance, 10MΩ Wide Supply Range, ±5V to ±15V Shutdown Mode: IS < 200µA Adjustable Supply Current Stable with CL = 10,000p Available in 8-Pin DIP and SO and 7-Pin DD and TO-220 Packages The LT1206 is manufactured on Linear Technology’s proprietary complementary bipolar process. APPLICATIONS ■ ■ ■ ■ ■ Video Amplifiers Cable Drivers RGB Amplifiers Test Equipment Amplifiers Buffers , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATION Noninverting Amplifier with Shutdown Large-Signal Response, CL = 10,000pF 15V VIN + VOUT LT1206 COMP CCOMP – S/D** 0.01µF* –15V RF 15V RG 5V 24k *OPTIONAL, USE WITH CAPACITIVE LOADS **GROUND SHUTDOWN PIN FOR NORMAL OPERATION ENABLE 74C906 LT1206 • TA01 VS = ±15V RL = RG = 3k RL = ∞ 500ns/DIV 1206 TA02 1206fa 1 LT1206 ABSOLUTE MAXIMUM RATINGS (Note 1) Supply Voltage ........................................................±18V Input Current........................................................±15mA Output Short-Circuit Duration (Note 2) .........Continuous Specified Temperature Range (Note 3) ........ 0°C to 70°C Operating Temperature Range ................. –40°C to 85°C Junction Temperature ........................................... 150°C Storage Temperature Range................... –65°C to 150°C Lead Temperature (Soldering, 10 sec) .................. 300°C PACKAGE/OERDER INFORMATION TOP VIEW TOP VIEW NC 1 8 V+ –IN 2 7 +IN 3 6 S/D* 4 5 COMP V+ 1 8 V+ OUT –IN 2 7 OUT V– +IN 3 6 V– S/D* 4 5 COMP S8 PACKAGE 8-LEAD PLASTIC SO θJA = 60°C/W N8 PACKAGE 8-LEAD PLASTIC DIP θJA = 100°C/W ORDER PART NUMBER ORDER PART NUMBER S8 PART MARKING LT1206CN8** LT1206CS8** 1206 FRONT VIEW TAB IS V+ FRONT VIEW 7 6 5 4 3 2 1 OUT V– COMP V+ S/D* +IN –IN OUT V– COMP V+ S/D* +IN –IN 7 6 5 4 3 2 1 TAB IS V+ T7 PACKAGE 7-LEAD PLASTIC TO-220 θJA = 5°C/W R PACKAGE 7-LEAD PLASTIC DD θJA = 30°C/W ORDER PART NUMBER ORDER PART NUMBER LT1206CR** LT1206CT7** Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marking: http://www.linear.com/leadfree/ Consult LTC Marketing for parts specified with wider operating temperature ranges. *Ground shutdown pin for normal operation. ** See Note 3. ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCM = 0, ±5V ≤ VS ≤ 15V, pulse tested, VS/D = 0V, unless otherwise noted. SYMBOL PARAMETER VOS Input Offset Voltage Input Offset Voltage Drift IIN + IIN– Noninverting Input Current Inverting Input Current CONDITIONS MIN ● ● ● ● TYP MAX UNITS ±3 ±10 ±15 mV mV µV/°C ±8 ±25 ±60 ±100 µA µA µA µA 10 ±2 ±10 1206fa 2 LT1206 ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCM = 0, ±5V ≤ VS ≤ 15V, pulse tested, VS/D = 0V, unless otherwise noted. SYMBOL PARAMETER CONDITIONS en Input Noise Voltage Density f = 10kHz, RF = 1k, RG = 10Ω, RS = 0Ω 3.6 nV/√Hz +in Input Noise Current Density f = 10kHz, RF = 1k, RG = 10Ω, RS = 10k 2 pA/√Hz –in Input Noise Current Density f = 10kHz, RF = 1k, RG = 10Ω, RS = 10k 30 pA/√Hz RIN Input Resistance ● ● 1.5 0.5 CIN Input Capacitance VIN = ±12V, VS = ±15V VIN = ±2V, VS = ±5V VS = ±15V 10 5 2 MΩ MΩ pF VS = ±15V VS = ±5V VS = ±15V, VCM = ±12V VS = ±5V, VCM = ±2V VS = ±15V, VCM = ±12V VS = ±5V, VCM = ±2V VS = ±5V to ±15V ● ● ±12 ±2 55 50 ±13.5 ±3.5 62 60 0.1 0.1 77 V V dB dB µA/V µA/V dB VS = ±5V to ±15V ● 30 500 nA/V VS = ±5V to ±15V ● 0.7 5 µA/V VS = ±15V, VOUT = ±10V, RL = 50Ω VS = ±5V, VOUT = ±2V, RL = 25Ω VS = ±15V, VOUT = ±10V, RL = 50Ω VS = ±5V, VOUT = ±2V, RL = 25Ω VS = ±15V, RL = 50Ω ● ● 500 1200 dB dB kΩ kΩ V V V V mA 20 30 35 17 mA mA mA Input Voltage Range CMRR Common Mode Rejection Ratio PSRR Inverting Input Current Common Mode Rejection Power Supply Rejection Ratio AV Noninverting Input Current Power Supply Rejection Inverting Input Current Power Supply Rejection Large-Signal Voltage Gain ROL Transresistance, ΔVOUT/ΔIIN– VOUT Maximum Output Voltage Swing MIN VS = ±15V, RL = 25Ω ● ● ● ● ● ● ● ● ● ● 60 55 55 100 75 ±11.5 ±10.0 ±2.5 ±2.0 250 TYP MAX 10 10 71 68 260 200 ±12.5 ±3.0 UNITS IOUT Maximum Output Current RL = 1Ω IS Supply Current VS = ±15V, VS/D = 0V Supply Current, RS/D = 51k (Note 4) VS = ±15V Positive Supply Current, Shutdown VS = ±15V, VS/D = 15V ● 200 µA Output Leakage Current, Shutdown VS = ±15V, VS/D = 15V ● 10 µA Slew Rate (Note 5) AV = 2 Differential Gain (Note 6) SR BW ● 12 900 V/µs VS = ±15V, RF = 560Ω, RG = 560Ω, RL = 30Ω 0.02 % Differential Phase (Note 6) VS = ±15V, RF = 560Ω, RG = 560Ω, RL = 30Ω 0.17 Deg Small-Signal Bandwidth VS = ±15V, Peaking ≤ 0.5dB, RF = RG = 620Ω, RL = 100Ω VS = ±15V, Peaking ≤ 0.5dB, RF = RG = 649Ω, RL = 50Ω VS = ±15V, Peaking ≤ 0.5dB, RF = RG = 698Ω, RL = 30Ω VS = ±15V, Peaking ≤ 0.5dB, RF = RG = 825Ω, RL = 10Ω 60 MHz 52 MHz 43 MHz 27 MHz Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: Applies to short circuits to ground only. A short circuit between the output and either supply may permanently damage the part when operated on supplies greater than ± 10V. 400 Note 3: Commercial grade parts are designed to operate over the temperature range of –40°C to 85°C but are neither tested nor guaranteed beyond 0°C to 70°C. Industrial grade parts tested over –40°C to 85°C are available on special request. Consult factory. Note 4: RS/D is connected between the shutdown pin and ground. Note 5: Slew rate is measured at ±5V on a ± 10V output signal while operating on ±15V supplies with RF = 1.5k, RG = 1.5k and RL = 400Ω. Note 6: NTSC composite video with an output level of 2V. 1206fa 3 LT1206 SMALL-SIGNAL BANDWIDTH IS = 20mA Typical, Peaking ≤ 0.1dB AV RL RF RG –3dB BW (MHz) –0.1dB BW (MHz) VS = ±5V, RS/D = 0Ω AV RL RF RG –3dB BW (MHz) –0.1dB BW (MHz) VS = ±15V, RS/D = 0Ω –1 150 30 10 562 649 732 562 649 732 48 34 22 21.4 17 12.5 –1 150 30 10 681 768 887 681 768 887 50 35 24 19.2 17 12.3 1 150 30 10 619 715 806 – – – 54 36 22.4 22.3 17.5 11.5 1 150 30 10 768 909 1k – – – 66 37 23 22.4 17.5 12 2 150 30 10 576 649 750 576 649 750 48 35 22.4 20.7 18.1 11.7 2 150 30 10 665 787 931 665 787 931 55 36 22.5 23 18.5 11.8 10 150 30 10 442 511 649 48.7 56.2 71.5 40 31 20 19.2 16.5 10.2 10 150 30 10 487 590 768 536 64.9 84.5 44 33 20.7 20.7 17.5 10.8 –3dB BW (MHz) –0.1dB BW (MHz) AV RL RF RG –3dB BW (MHz) –0.1dB BW (MHz) IS = 10mA Typical, Peaking ≤ 0.1dB AV RL RF RG VS = ±5V, RS/D = 10.2k VS = ±15V, RS/D = 60.4k –1 150 30 10 576 681 750 576 681 750 35 25 16.4 17 12.5 8.7 –1 150 30 10 634 768 866 634 768 866 41 26.5 17 19.1 14 9.4 1 150 30 10 665 768 845 – – – 37 25 16.5 17.5 12.6 8.2 1 150 30 10 768 909 1k – – – 44 28 16.8 18.8 14.4 8.3 2 150 30 10 590 681 768 590 681 768 35 25 16.2 16.8 13.4 8.1 2 150 30 10 649 787 931 649 787 931 40 27 16.5 18.5 14.1 8.1 10 150 30 10 301 392 499 33.2 43.2 54.9 31 23 15 15.6 11.9 7.8 10 150 30 10 301 402 590 33.2 44.2 64.9 33 25 15.3 15.6 13.3 7.4 RG –3dB BW (MHz) –0.1dB BW (MHz) AV RL RF RG –3dB BW (MHz) –0.1dB BW (MHz) IS = 5mA Typical, Peaking ≤ 0.1dB AV RL RF VS = ±5V, RS/D = 22.1k VS = ±15V, RS/D = 121k –1 150 30 10 604 715 681 604 715 681 21 14.6 10.5 10.5 7.4 6.0 –1 150 30 10 619 787 825 619 787 825 25 15.8 10.5 12.5 8.5 5.4 1 150 30 10 768 866 825 – – – 20 14.1 9.8 9.6 6.7 5.1 1 150 30 10 845 1k 1k – – – 23 15.3 10 10.6 7.6 5.2 2 150 30 10 634 750 732 634 750 732 20 14.1 9.6 9.6 7.2 5.1 2 150 30 10 681 845 866 681 845 866 23 15 10 10.2 7.7 5.4 10 150 30 10 100 100 100 11.1 11.1 11.1 16.2 13.4 9.5 5.8 7.0 4.7 10 150 30 10 100 100 100 11.1 11.1 11.1 15.9 13.6 9.6 4.5 6 4.5 1206fa 4 LT1206 TYPICAL PERFORMANCE CHARACTERISTICS 100 RF = 560Ω 60 RF = 680Ω 50 40 RF = 750Ω 30 RF = 1k 20 10 40 FEEDBACK RESISTOR (Ω) –3dB BANDWIDTH (MHz) RF = 470Ω RF = 560Ω 30 RF = 750Ω 20 RF = 1k RF = 2k 10 1k FEEDBACK RESISTOR AV = 2 RL = ∞ VS = ±15V CCOMP = 0.01µF 10 RF = 1.5k 0 100 0 4 14 12 10 8 SUPPLY VOLTAGE (±V) 6 16 4 18 6 14 12 10 8 SUPPLY VOLTAGE (±V) LT1206 • TPC01 16 Bandwidth and Feedback Resistance vs Capacitive Load for 5dB Peak 50 70 RF =390Ω 60 RF = 330Ω 50 40 RF = 470Ω 30 RF = 680Ω 20 10 AV = 10 RL = 10Ω BANDWIDTH 40 30 RF = 560Ω 20 RF = 680Ω RF = 1k 10 10 1k FEEDBACK RESISTOR RF = 1.5k RF = 1.5k 0 4 14 12 10 8 SUPPLY VOLTAGE (±V) 6 16 100 0 0 4 18 6 14 12 10 8 SUPPLY VOLTAGE (±V) LT1206 • TPC04 16 18 1 Spot Noise Voltage and Current vs Frequency 100 0.10 0.20 RL = 30Ω RL = 50Ω 0.10 RL = 15Ω 0.08 DIFFERENTIAL GAIN (%) RF = RG = 560Ω AV = 2 N PACKAGE RF = RG = 560Ω AV = 2 N PACKAGE SPOT NOISE (nV/√Hz OR pA/√Hz) RL = 15Ω 0.06 RL = 30Ω 0.04 RL = 50Ω 0.02 RL = 150Ω 0 7 11 13 9 SUPPLY VOLTAGE (±V) 15 LT1206 • TPC07 –in 10 en in RL = 150Ω 0 5 1 10k LT1206 • TPC06 Differential Gain vs Supply Voltage 0.50 0.30 10 100 1k CAPACITIVE LOAD (pF) LT1206 • TPC05 Differential Phase vs Supply Voltage 0.40 AV = +2 RL = ∞ VS = ±15V CCOMP = 0.01µF –3dB BANDWIDTH (MHz) – 3dB BANDWIDTH (MHz) 80 100 10k PEAKING ≤ 0.5dB PEAKING ≤ 5dB AV = 10 RL = 100Ω FEEDBACK RESISTOR (Ω) PEAKING ≤ 0.5dB PEAKING ≤ 5dB 1 10000 LT1206 • TPC03 Bandwidth vs Supply Voltage 100 90 100 10 1000 CAPACITIVE LOAD (pF) 1 18 LT1206 • TPC02 Bandwidth vs Supply Voltage –3dB BANDWIDTH (MHz) BANDWIDTH AV = 2 RL = 10Ω –3dB BANDWIDTH (MHz) – 3dB BANDWIDTH (MHz) PEAKING ≤ 0.5dB PEAKING ≤ 5dB AV = 2 RL = 100Ω 80 70 100 10k 50 PEAKING ≤ 0.5dB PEAKING ≤ 5dB 90 DIFFERENTIAL PHASE (DEG) Bandwidth and Feedback Resistance vs Capacitive Load for 0.5dB Peak Bandwidth vs Supply Voltage Bandwidth vs Supply Voltage 5 7 11 13 9 SUPPLY VOLTAGE (±V) 15 LT1206 • TPC08 1 10 100 1k 10k FREQUENCY (Hz) 100k LT1206 • TPC09 1206fa 5 LT1206 TYPICAL PERFORMANCE CHARACTERISTICS Supply Current vs Ambient Temperature, VS = ±5V Supply Current vs Supply Voltage 24 25 25 TJ = –40˚C 22 RSD = 0Ω SUPPLY CURRENT (mA) 20 20 TJ = 25˚C 18 16 TJ = 85˚C 14 TJ = 125˚C AV = 1 RL = ∞ N PACKAGE 15 RSD = 10.2k 10 RSD = 22.1k 5 AV = 1 RL = ∞ N PACKAGE RSD = 0Ω 20 SUPPLY CURRENT (mA) VS/D = 0V SUPPLY CURRENT (mA) Supply Current vs Ambient Temperature, VS = ±15V 15 RSD = 60.4k 10 RSD = 121k 5 12 0 –50 –25 10 4 16 14 12 10 8 SUPPLY VOLTAGE (±V) 6 18 50 25 0 75 TEMPERATURE (°C) Supply Current vs Shutdown Pin Current OUTPUT SHORT-CIRCUIT CURRENT (A) COMMON-MODE RANGE (V) 14 12 10 8 6 4 –1.0 –1.5 –2.0 2.0 1.5 1.0 0.5 2 100 300 400 200 SHUTDOWN PIN CURRENT (µA) 0 V– –50 500 –25 LT1206 • TPC13 –2 –3 –4 4 RL = 50Ω 2 RL = 2k 1 V– –50 –25 0.6 SINKING 0.5 0.4 0.3 –50 –25 0 75 25 50 TEMPERATURE (°C) 100 125 LT1206 • TPC16 50 25 75 0 TEMPERATURE (°C) 60 50 100 125 LT1206 • TPC15 Supply Current vs Large-Signal Output Frequency (No Load) 60 70 RL = 2k RL = 50Ω 3 SOURCING 0.7 Power Supply Rejection Ratio vs Frequency POWER SUPPLY REJECTION (dB) OUTPUT SATURATION VOLTAGE (V) –1 125 0.8 LT1206 • TPC14 Output Saturation Voltage vs Junction Temperature VS = ±15V 100 0 75 25 50 TEMPERATURE (°C) 0.9 NEGATIVE RL = 50Ω VS = ±15V RF = RG = 1k 50 SUPPLY CURRENT (mA) SUPPLY CURRENT (mA) 1.0 – 0.5 16 V+ Output Short-Circuit Current vs Junction Temperature V+ VS = ±15V 125 100 LT1206 • TPC12 Input Common Mode Limit vs Junction Temperature 20 18 50 25 0 75 TEMPERATURE (°C) LT1206 • TPC11 LT1206 • TPC10 0 0 –50 –25 125 100 POSITIVE 40 30 20 AV = 2 RL = ∞ VS = ±15V VOUT = 20VP-P 40 30 20 10 0 10k 100k 1M 10M FREQUENCY (Hz) 100M 10 10k 100k 1M 10M FREQUENCY (Hz) LT1206 • TPC17 LT1206 • TPC18 1206fa 6 LT1206 TYPICAL PERFORMANCE CHARACTERISTICS Output Impedance in Shutdown vs Frequency Output Impedance vs Frequency –30 100k VS = ±15V IO = 0mA AV = 1 RF = 1k VS = ±15V RS/D = 0Ω 1 0.1 VS = ±15V VO = 2VP-P –40 2nd RL = 10Ω 10k DISTORTION (dBc) RS/D = 121k 10 OUTPUT IMPEDANCE (Ω) OUTPUT IMPEDANCE (Ω) 100 2nd and 3rd Harmonic Distortion vs Frequency 1k –50 3rd 2nd –60 –70 RL = 30Ω 100 3rd –80 10M 1M 100M –90 10 100k 1M FREQUENCY (Hz) 10M 100M 1 3 2 4 5 FREQUENCY (MHz) FREQUENCY (Hz) LT1206 • TPC19 Test Circuit for 3rd Order Intercept VS = ±15V RL = 50Ω RF = 590Ω RG = 64.9Ω 50 6 7 8 9 10 LT1206 • TPC21 LT1206 • TPC20 3rd Order Intercept vs Frequency 60 3rd ORDER INTERCEPT (dBm) 0.01 100k + PO LT1206 – 40 590Ω 30 50Ω 65Ω MEASURE INTERCEPT AT PO LT1206 • TPC23 20 10 0 5 10 15 20 FREQUENCY (MHz) 25 30 LT1206 • TPC22 1206fa 7 LT1206 SIMPLIFIED SCHEMATIC V+ TO ALL CURRENT SOURCES Q5 Q10 Q2 Q18 Q17 D1 Q6 Q1 Q11 Q15 Q9 V– 1.25k +IN CC –IN V– 50Ω COMP RC OUTPUT V+ SHUTDOWN V+ Q12 Q3 Q8 Q16 Q14 D2 Q4 Q13 Q7 V– LT1206 • SS APPLICATIONS INFORMATION The LT1206 is a current feedback amplifier with high output current drive capability. The device is stable with large capacitive loads and can easily supply the high currents required by capacitive loads. The amplifier will drive low impedance loads such as cables with excellent linearity at high frequencies. Feedback Resistor Selection The optimum value for the feedback resistors is a function of the operating conditions of the device, the load impedance and the desired flatness of response. The Typical AC Performance tables give the values which result in the highest 0.1dB and 0.5dB bandwidths for various resistive loads and operating conditions. If this level of flatness is not required, a higher bandwidth can be obtained by use of a lower feedback resistor. The characteristic curves of Bandwidth vs Supply Voltage indicate feedback resistors for peaking up to 5dB. These curves use a solid line when the response has less than 0.5dB of peaking and a dashed line when the response has 0.5dB to 5dB of peaking. The curves stop where the response has more than 5dB of peaking. For resistive loads, the COMP pin should be left open (see section on capacitive loads). Capacitive Loads The LT1206 includes an optional compensation network for driving capacitive loads. This network eliminates most of the output stage peaking associated with capacitive loads, allowing the frequency response to be flattened. Figure 1 shows the effect of the network on a 200pF load. Without the optional compensation, there is a 5dB peak at 40MHz caused by the effect of the capacitance on the output stage. Adding a 0.01µF bypass capacitor between the output and the COMP pins connects the compensation and completely eliminates the peaking. A lower value feedback resistor can now be used, resulting in a response which 1206fa 8 LT1206 APPLICATIONS INFORMATION 12 VS = ±15V 10 RF = 1.2k COMPENSATION VOLTAGE GAIN (dB) 8 6 4 RF = 2k NO COMPENSATION 2 0 RF = 2k COMPENSATION –2 –4 –6 –8 1 10 FREQUENCY (MHz) 100 LT1206 • F01 Figure 1 is flat to 0.35dB to 30MHz. The network has the greatest effect for CL in the range of 0pF to 1000pF. The graph of Maximum Capacitive Load vs Feedback Resistor can be used to select the appropriate value of feedback resistor. The values shown are for 0.5dB and 5dB peaking at a gain of 2 with no resistive load. This is a worst case condition, as the amplifier is more stable at higher gains and with some resistive load in parallel with the capacitance. Also shown is the – 3dB bandwidth with the suggested feedback resistor vs the load capacitance. capacitor and the supply current is typically 100µA. The shutdown pin is referenced to the positive supply through an internal bias circuit (see the simplified schematic). An easy way to force shutdown is to use open drain (collector) logic. The circuit shown in Figure 2 uses a 74C904 buffer to interface between 5V logic and the LT1206. The switching time between the active and shutdown states is less than 1µs. A 24k pull-up resistor speeds up the turn-off time and insures that the LT1206 is completely turned off. Because the pin is referenced to the positive supply, the logic used should have a breakdown voltage of greater than the positive supply voltage. No other circuitry is necessary as the internal circuit limits the shutdown pin current to about 500µA. Figure 3 shows the resulting waveforms. 15V VOUT LT1206 – S/D –15V RF 15V 5V Although the optional compensation works well with capacitive loads, it simply reduces the bandwidth when it is connected with resistive loads. For instance, with a 30Ω load, the bandwidth drops from 55MHz to 35MHz when the compensation is connected. Hence, the compensation was made optional. To disconnect the optional compensation, leave the COMP pin open. Shutdown/Current Set + VIN RG 24k ENABLE LT1206 • F02 74C906 Figure 2. Shutdown Interface VOUT If the shutdown feature is not used, the SHUTDOWN pin must be connected to ground or V –. The shutdown pin can be used to either turn off the biasing for the amplifier, reducing the quiescent current to less than 200µA, or to control the quiescent current in normal operation. The total bias current in the LT1206 is controlled by the current flowing out of the shutdown pin. When the shutdown pin is open or driven to the positive supply, the part is shut down. In the shutdown mode, the output looks like a 40pF ENABLE AV = 1 RF = 825Ω RL = 50Ω RPU = 24k VIN = 1VP-P 1µs/DIV 1206 F03 Figure 3. Shutdown Operation 1206fa 9 LT1206 APPLICATIONS INFORMATION For applications where the full bandwidth of the amplifier is not required, the quiescent current of the device may be reduced by connecting a resistor from the shutdown pin to ground. The quiescent current will be approximately 40 times the current in the shutdown pin. The voltage across the resistor in this condition is V + – 3VBE. For example, a 60k resistor will set the quiescent supply current to 10mA with VS = ±15V. The photos (Figures 4a and 4b) show the effect of reducing the quiescent supply current on the large-signal response. The quiescent current can be reduced to 5mA in the inverting configuration without much change in response. In noninverting mode, however, the slew rate is reduced as the quiescent current is reduced. RF = 750Ω RL = 50Ω IQ = 5mA, 10mA, 20mA VS = ±15V 50ns/DIV Slew Rate Unlike a traditional op amp, the slew rate of a current feedback amplifier is not independent of the amplifier gain configuration. There are slew rate limitations in both the input stage and the output stage. In the inverting mode, and for higher gains in the noninverting mode, the signal amplitude on the input pins is small and the overall slew rate is that of the output stage. The input stage slew rate is related to the quiescent current and will be reduced as the supply current is reduced. The output slew rate is set by the value of the feedback resistors and the internal capacitance. Larger feedback resistors will reduce the slew rate as will lower supply voltages, similar to the way the bandwidth is reduced. The photos (Figures 5a, 5b and 5c) show the large-signal response of the LT1206 for various gain configurations. The slew rate varies from 860V/µs for a gain of 1, to 1400V/µs for a gain of – 1. 1206 F04a Figure 4a. Large-Signal Response vs IQ, AV = –1 RF = 825Ω RL = 50Ω VS = ±15V 20ns/DIV 1206 F05a Figure 5a. Large-Signal Response, AV = 1 RF = 750Ω RL = 50Ω IQ = 5mA, 10mA, 20mA VS = ±15V 50ns/DIV 1206 F04b Figure 4b. Large-Signal Response vs IQ, AV = 2 RF = RG = 750Ω RL = 50Ω VS = ±15V 20ns/DIV 1206 F05b Figure 5a. Large-Signal Response, AV = –1 1206fa 10 LT1206 APPLICATIONS INFORMATION the maximum allowable input voltage. To allow for some margin, it is recommended that the input signal be less than ±5V when the device is shut down. Capacitance on the Inverting Input RF = 750Ω RL = 50Ω 20ns/DIV 1206 F05c Figure 5c. Large-Signal Response, AV = 2 When the LT1206 is used to drive capacitive loads, the available output current can limit the overall slew rate. In the fastest configuration, the LT1206 is capable of a slew rate of over 1V/ns. The current required to slew a capacitor at this rate is 1mA per picofarad of capacitance, so 10,000pF would require 10A! The photo (Figure 6) shows the large signal behavior with CL = 10,000pF. The slew rate is about 60V/µs, determined by the current limit of 600mA. Current feedback amplifiers require resistive feedback from the output to the inverting input for stable operation. Take care to minimize the stray capacitance between the output and the inverting input. Capacitance on the inverting input to ground will cause peaking in the frequency response (and overshoot in the transient response), but it does not degrade the stability of the amplifier. Power Supplies The LT1206 will operate from single or split supplies from ± 5V (10V total) to ±15V (30V total). It is not necessary to use equal value split supplies, however the offset voltage and inverting input bias current will change. The offset voltage changes about 500µV per volt of supply mismatch. The inverting bias current can change as much as 5µA per volt of supply mismatch, though typically the change is less than 0.5µA per volt. Thermal Considerations VS = ±15V RL = RG = 3k RL = ∞ 500ns/DIV 1206 TA02 Figure 6. Large-Signal Response, CL = 10,000pF Differential Input Signal Swing The differential input swing is limited to about ± 6V by an ESD protection device connected between the inputs. In normal operation, the differential voltage between the input pins is small, so this clamp has no effect; however, in the shutdown mode the differential swing can be the same as the input swing. The clamp voltage will then set The LT1206 contains a thermal shutdown feature which protects against excessive internal (junction) temperature. If the junction temperature of the device exceeds the protection threshold, the device will begin cycling between normal operation and an off state. The cycling is not harmful to the part. The thermal cycling occurs at a slow rate, typically 10ms to several seconds, which depends on the power dissipation and the thermal time constants of the package and heat sinking. Raising the ambient temperature until the device begins thermal shutdown gives a good indication of how much margin there is in the thermal design. For surface mount devices heat sinking is accomplished by using the heat spreading capabilities of the PC board and its copper traces. Experiments have shown that the heat spreading copper layer does not need to be electrically connected to the tab of the device. The PCB material can be very effective at transmitting heat between the pad area attached to the tab of the device, and a ground or 1206fa 11 LT1206 APPLICATIONS INFORMATION power plane layer either inside or on the opposite side of the board. Although the actual thermal resistance of the PCB material is high, the length/area ratio of the thermal resistance between the layer is small. Copper board stiffeners and plated through holes can also be used to spread the heat generated by the device. Tables 1 and 2 list thermal resistance for each package. For the TO-220 package, thermal resistance is given for junction-to-case only since this package is usually mounted to a heat sink. Measured values of thermal resistance for several different board sizes and copper areas are listed for each surface mount package. All measurements were taken in still air on 3/32" FR-4 board with 1oz copper. This data can be used as a rough guideline in estimating thermal resistance. The thermal resistance for each application will be affected by thermal interactions with other components as well as board size and shape. Table 1. R Package, 7-Lead DD COPPER AREA THERMAL RESISTANCE TOPSIDE* BACKSIDE BOARD AREA (JUNCTION-TO-AMBIENT) 2500 sq. mm 2500 sq. mm 2500 sq. mm 1000 sq. mm 2500 sq. mm 2500 sq. mm 125 sq. mm 2500 sq. mm 2500 sq. mm *Tab of device attached to topside copper Y Package, 7-Lead TO-220 Thermal Resistance (Junction-to-Case) = 5°C/W N8 Package, 8-Lead DIP Thermal Resistance (Junction-to-Ambient) = 100°C/W The junction temperature can be calculated from the equation: TJ = (PD × θJA) + TA where: TJ = Junction Temperature TA = Ambient Temperature PD = Device Dissipation θJA = Thermal Resistance (Junction-to Ambient) As an example, calculate the junction temperature for the circuit in Figure 7 for the N8, S8, and R packages assuming a 70°C ambient temperature. 15V I 39mA + 330Ω 12V LT1206 S/D – f = 2MHz 0.01µF 2k 25°C/W 27°C/W 35°C/W –15V –12V 300pF 2k LT1206 • F07 Figure 7. Thermal Calculation Example Table 2. S8 Package, 8-Lead Plastic SO COPPER AREA THERMAL RESISTANCE TOPSIDE* BACKSIDE BOARD AREA (JUNCTION-TO-AMBIENT) 2500 sq. mm 2500 sq. mm 2500 sq. mm 1000 sq. mm 2500 sq. mm 2500 sq. mm 225 sq. mm 2500 sq. mm 2500 sq. mm 100 sq. mm 2500 sq. mm 2500 sq. mm 100 sq. mm 1000 sq. mm 2500 sq. mm 100 sq. mm 225 sq. mm 2500 sq. mm 100 sq. mm 100 sq. mm 2500 sq. mm *Pins 1 and 2 attached to topside copper Calculating Junction Temperature 60°C/W 62°C/W 65°C/W 69°C/W 73°C/W 80°C/W 83°C/W The device dissipation can be found by measuring the supply currents, calculating the total dissipation, and then subtracting the dissipation in the load and feedback network. PD = (39mA × 30V) – (12V)2/(2k||2k) = 1.03W Then: TJ = (1.03W × 100°C/W) + 70°C = 173°C for the N8 package TJ = (1.03W × 65°C/W) × + 70°C = 137°C for the S8 with 225 sq. mm topside heat sinking TJ = (1.03W × 35°C/W) × + 70°C = 106°C for the R package with 100 sq. mm topside heat sinking Since the Maximum Junction Temperature is 150°C, the N8 package is clearly unacceptable. Both the S8 and R packages are usable. 1206fa 12 LT1206 TYPICAL APPLICATIONS Precision ×10 Hi Current Amplifier CMOS Logic to Shutdown Interface 15V + + LT1097 LT1206 COMP – S/D – + OUT 330Ω 24k LT1206 S/D 0.01µF – 500pF LT1206 • TA05 3k 5V –15V 10k 2N3904 10k LT1206 • TA03 OUTPUT OFFSET: < 500µV SLEW RATE: 2V/µs BANDWIDTH: 4MHz STABLE WITH CL < 10nF 1k Low Noise ×10 Buffered Line Driver 15V 1µF + + 75Ω + 1µF – + VIN + LT1115 – Distribution Amplifier 15V 1µF + – OUTPUT LT1206 S/D 75Ω CABLE 75Ω RF 75Ω 0.01µF RL LT1206 • TA06 RG –15V 1µF 68pF 75Ω LT1206 S/D 75Ω + VIN –15V 560Ω 560Ω 909Ω LT1206 • TA04 100Ω RL = 32Ω VO = 5VRMS THD + NOISE = 0.0009% AT 1kHz = 0.004% AT 20kHz SMALL SIGNAL 0.1dB BANDWIDTH = 600kHz Buffer AV = 1 VIN + LT1206 COMP S/D – VOUT 0.01µF* *OPTIONAL, USE WITH CAPACITIVE LOADS **VALUE OF RF DEPENDS ON SUPPLY VOLTAGE AND LOADING. SELECT FROM TYPICAL AC PERFORMANCE TABLE OR DETERMINE EMPIRICALLY RF** LT1206 • TA07 1206fa 13 LT1206 PACKAGE DESCRIPTION N8 Package 8-Lead PDIP (Narrow .300 Inch) (Reference LTC DWG # 05-08-1510) .300 – .325 (7.620 – 8.255) ( +0.889 8.255 –0.381 .130 ± .005 (3.302 ± 0.127) .045 – .065 (1.143 – 1.651) .065 (1.651) TYP .008 – .015 (0.203 – 0.381) +.035 .325 –.015 .400* (10.160) MAX 8 7 6 5 1 2 3 4 .255 ± .015* (6.477 ± 0.381) ) .120 (3.048) .020 MIN (0.508) MIN .018 ± .003 (0.457 ± 0.076) .100 (2.54) BSC N8 1002 NOTE: 1. DIMENSIONS ARE INCHES MILLIMETERS *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .010 INCH (0.254mm) R Package 7-Lead Plastic DD Pak (Reference LTC DWG # 05-08-1462) .256 (6.502) .060 (1.524) TYP .060 (1.524) .390 – .415 (9.906 – 10.541) .165 – .180 (4.191 – 4.572) .045 – .055 (1.143 – 1.397) 15° TYP .060 (1.524) .183 (4.648) +.008 .004 –.004 +0.203 0.102 –0.102 .059 (1.499) TYP .330 – .370 (8.382 – 9.398) ( ) .095 – .115 (2.413 – 2.921) .075 (1.905) .300 (7.620) +.012 .143 –.020 +0.305 3.632 –0.508 ( BOTTOM VIEW OF DD PAK HATCHED AREA IS SOLDER PLATED COPPER HEAT SINK ) .026 – .035 (0.660 – 0.889) TYP .050 (1.27) BSC .013 – .023 (0.330 – 0.584) .050 ± .012 (1.270 ± 0.305) R (DD7) 0502 .420 .080 .420 .276 .350 .325 .205 .565 .565 .320 .090 .050 .035 RECOMMENDED SOLDER PAD LAYOUT NOTE: 1. DIMENSIONS IN INCH/(MILLIMETER) 2. DRAWING NOT TO SCALE .090 .050 .035 RECOMMENDED SOLDER PAD LAYOUT FOR THICKER SOLDER PASTE APPLICATIONS 1206fa 14 LT1206 PACKAGE DESCRIPTION S8 Package 8-Lead Plastic Small Outline (Narrow .150 Inch) (Reference LTC DWG # 05-08-1610) .189 – .197 (4.801 – 5.004) NOTE 3 .045 ±.005 .050 BSC 7 8 .245 MIN 6 5 .160 ±.005 .150 – .157 (3.810 – 3.988) NOTE 3 .228 – .244 (5.791 – 6.197) .030 ±.005 TYP 1 RECOMMENDED SOLDER PAD LAYOUT .010 – .020 × 45° (0.254 – 0.508) 3 2 4 .053 – .069 (1.346 – 1.752) .008 – .010 (0.203 – 0.254) .004 – .010 (0.101 – 0.254) 0°– 8° TYP .016 – .050 (0.406 – 1.270) .050 (1.270) BSC .014 – .019 (0.355 – 0.483) TYP NOTE: 1. DIMENSIONS IN INCHES (MILLIMETERS) 2. DRAWING NOT TO SCALE 3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm) SO8 0303 T7 Package 7-Lead Plastic TO-220 (Standard) (Reference LTC DWG # 05-08-1422) .390 – .415 (9.906 – 10.541) .165 – .180 (4.191 – 4.572) .147 – .155 (3.734 – 3.937) DIA .045 – .055 (1.143 – 1.397) .230 – .270 (5.842 – 6.858) .460 – .500 (11.684 – 12.700) .570 – .620 (14.478 – 15.748) .330 – .370 (8.382 – 9.398) .620 (15.75) TYP .700 – .728 (17.780 – 18.491) .095 – .115 (2.413 – 2.921) .155 – .195* (3.937 – 4.953) SEATING PLANE .152 – .202 .260 – .320 (3.860 – 5.130) (6.604 – 8.128) BSC .050 (1.27) .026 – .036 (0.660 – 0.914) .135 – .165 (3.429 – 4.191) .013 – .023 (0.330 – 0.584) *MEASURED AT THE SEATING PLANE T7 (TO-220) 0801 1206fa Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 15 LT1206 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1010 High Speed Buffer High Power, High Speed Buffer LT1207 Dual 250mA Out, 900V/µs, 60MHz Current Feedback Amplifier Adjustable Supply Current, Shutdown LT1210 1.1A, 35MHz, 900V/µs Current Feedback Amplifier Adjustable Supply Current, Shutdown LT1395 Single 400MHz Current Feedback Amplifier 0.1dB Gain Flatness to 100MHz LT1815 6.5mA, 220MHz, 1.5V/ns Operational Amplifier with Programmable Current S6 Version Features Programmable Supply Current LT1818 400MHz, 2500V/µs, 9mA Single Operational Amplifier High Speed, Low Noise, Low Distortion, Low Offset 1206fa 16 Linear Technology Corporation LT 0307 REV A • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 1993