LT1189 Low Power Video Difference Amplifier U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Differential or Single-Ended Gain Block (Adjustable) –3dB Bandwidth, AV = ±10 35MHz Slew Rate 220V/µs Low Supply Current 13mA Output Current ± 20mA CMRR at 10MHz 48dB LT1193 Pin Out Low Cost Single 5V Operation Drives Cables Directly Output Shutdown UO APPLICATI ■ ■ ■ The LT1189’s high slew rate, 220V/µs, wide bandwidth, 35MHz, and ±20mA output current require only 13mA of supply current. The shutdown feature reduces the power dissipation to a mere 15mW, and allows multiple amplifiers to drive the same cable. The LT1189 is a low power, gain of 10 stable version of the popular LT1193, and is available in 8-pin miniDIPs and SO packages. For lower gain applications see the LT1187 data sheet. Line Receivers Video Signal Processing Cable Drivers Tape and Disc Drive Systems UO ■ S The LT1189 is a difference amplifier optimized for operation on ±5V, or a single 5V supply, and gain ≥ 10. This versatile amplifier features uncommitted high input impedance (+) and (–) inputs, and can be used in differential or single-ended configurations. Additionally, a second set of inputs give gain adjustment and DC control to the difference amplifier. TYPICAL APPLICATI Cable Sense Amplifier for Loop Through Connections with DC Adjust Closed-Loop Gain vs Frequency 50 VIN 5V CABLE 2 VDC 1 8 + 40 7 – LT1189 + – 6 VOUT 4 –5V 909Ω VOLTAGE GAIN (dB) 3 VS = ±5V RL = 1k 30 20 10 100Ω 0 0.1 LT1189 • TA01 1 10 FREQUENCY (MHz) 100 LT1189 • TA02 1 LT1189 U U RATI GS W W W W AXI U U ABSOLUTE PACKAGE/ORDER I FOR ATIO Total Supply Voltage (V + to V –) ............................. 18V Differential Input Voltage ........................................ ±6V Input Voltage .......................................................... ±VS Output Short Circuit Duration (Note 1) ........ Continuous Operating Temperature Range LT1189M ..................................... – 55°C to 150°C LT1189C............................................. 0°C to 70°C Junction Temperature (Note 2) Plastic Package (CN8,CS8) ......................... 150°C Ceramic Package (CJ8,MJ8) ....................... 175°C Storage Temperature Range ................ – 65°C to 150°C Lead Temperature (Soldering, 10 sec.)................ 300°C ORDER PART NUMBER TOP VIEW +/REF 1 8 –/FB –IN 2 7 V+ +IN 3 6 OUT V– 4 5 S/D LT1189MJ8 LT1189CJ8 LT1189CN8 LT1189CS8 J8 PACKAGE N8 PACKAGE 8-LEAD HERMETIC DIP 8-LEAD PLASTIC DIP S8 PACKAGE 8-LEAD PLASTIC SOIC LT1189 • POI01 S8 PART MARKING TJMAX = 175°C, θJA = 100°C/W (J8) TJMAX = 150°C, θJA = 100°C/W (N8) TJMAX = 150°C, θJA = 150°C/W (S8) 1189 + –5V ELECTRICAL CHARACTERISTICS TA = 25°C, (Note 3) VS = ±5V, VREF = 0V, RFB1 = 900Ω from pins 6 to 8, RFB2 = 100Ω from pin 8 to ground, RL = RFB1 + RFB2 = 1k, CL ≤ 10pF, pin 5 open. PARAMETER Input Offset Voltage CONDITIONS Either Input, (Note 4) SOIC Package IOS Input Offset Current Either Input 0.2 1.0 IB Input Bias Current Either Input ±0.5 ±2.0 en Input Noise Voltage fO = 10kHz 30 nV/√Hz in Input Noise Current fO = 10kHz 1.25 pA/√Hz RIN Input Resistance Differential 30 kΩ CIN VIN LIM Input Capacitance Input Voltage Limit Either Input (Note 5) 2.0 ±170 pF mV Input Voltage Range MIN LT1189M/C TYP MAX 1.0 3.0 1.0 4.0 SYMBOL VOS –2.5 3.5 UNITS mV mV µA µA V CMRR Common-Mode Rejection Ratio VCM = –2.5V to 3.5V 80 105 dB PSRR Power Supply Rejection Ratio VS = ± 2.375V to ±8V 75 90 dB VOUT Output Voltage Swing VS = ± 5V, RL = 1k, AV = 50 ±3.8 ±4.0 V VS = ± 8V, RL = 1k, AV = 50 ±6.7 ±7.0 VS = ±8V, RL = 300Ω, AV = 50, (Note 3) ±6.4 ± 6.8 VO = ±1.0V, AV = 10 (Note 6, 10) 150 1.0 220 GE SR Gain Error Slew Rate FPBW Full Power Bandwidth VO = 2VP-P, (Note 7) 35 MHz BW Small Signal Bandwidth AV = 10 35 MHz tr, tf Rise Time, Fall Time tPD Propagation Delay AV = 50, VO = ±1.5V, 20% to 80% (Note 10) RL= 1k, VO = ±125mV, 50% to 50% Overshoot VO = ± 50mV ts Settling Time 3V Step, 0.1%, (Note 8) Diff AV Diff Ph Differential Gain Differential Phase RL = 1k, AV = 10, (Note 9) RL = 1k, AV = 10, (Note 9) IS Supply Current Shutdown Supply Current 2 Pin 5 at V – 35 50 3.5 75 % V/µs ns 12 ns 10 % 1 µs 0.6 0.75 % DEGP-P 13 16 mA 0.8 1.5 mA LT1189 + –5V ELECTRICAL CHARACTERISTICS TA = 25°C, (Note 3) VS = ±5V, VREF = 0V, RFB1 = 900Ω from pins 6 to 8, RFB2 = 100Ω from pin 8 to ground, RL = RFB1 + RFB2 = 1k, CL ≤ 10pF, pin 5 open. SYMBOL PARAMETER CONDITIONS Shutdown Pin Current Pin 5 at V – ton Turn On Time toff Turn Off Time Pin 5 from V – to Ground, RL = 1k Pin 5 from Ground to V –, RL = 1k IS/D MIN LT1189M/C TYP MAX 5 UNITS µA 25 500 ns 600 ns 5V CHARACTERISTICS ELECTRICAL + – TA = 25°C, (Note 3) VS = 5V, VS = 0V, VREF = 2.5V, RFB1 = 900Ω from pins 6 to 8, RFB2 = 100Ω from pin 8 to VREF, RL = RFB1 + RFB2 = 1k, CL ≤ 10pF, pin 5 open. MIN LT1189M/C TYP MAX SYMBOL PARAMETER CONDITIONS VOS Input Offset Voltage Either Input, (Note 4) SOIC Package 1.0 1.0 3.0 5.0 mV mV IOS Input Offset Current Either Input 0.2 1.0 µA IB Input Bias Current Either Input ± 0.5 ± 2.0 µA 3.5 V Input Voltage Range 2.0 CMRR Common-Mode Rejection Ratio VCM = 2.0V to 3.5V VOUT Output Voltage Swing RL = 300Ω to Ground (Note 3) SR Slew Rate VO = 1.5V to 3.5V BW Small-Signal Bandwidth AV = 10 IS Supply Current IS/D 80 VOUT High 3.6 VOUT Low dB 4.0 0.15 V 0.4 175 V/µs 30 MHz 12 15 mA Shutdown Supply Current Pin 5 at V – 0.8 1.5 mA Shutdown Pin Current Pin 5 at V – 5 25 µA + – 5V ELECTRICAL CHARACTERISTICS –55°C ≤ TA ≤ 125°C, (Note 3) V = ±5V, V = 0V, R = 900Ω from pins 6 to 8, R = 100Ω from pin 8 to ground, R = R + R S 100 UNITS REF FB1 FB2 L FB1 FB2 = MIN 1k, CL ≤ 10pF, pin 5 open. LT1189M TYP MAX SYMBOL PARAMETER CONDITIONS VOS Input Offset Voltage Either Input, (Note 4) 1.0 7.5 UNITS mV ∆VOS /∆T Input VOS Drift IOS Input Offset Current Either Input 0.2 1.5 µV/°C µA IB Input Bias Current Either Input ± 0.5 ±3.5 µA 10 Input Voltage Range –2.5 3.5 V CMRR Common-Mode Rejection Ratio VCM = –2.5V to 3.5V 80 105 dB PSRR Power Supply Rejection Ratio VS = ±2.375V to ±8V 65 90 dB VOUT Output Voltage Swing VS = ±5V, RL = 1k, AV = 50 ±3.7 ± 4.0 V VS = ±8V, RL = 1k, AV = 50 ±6.6 ±7.0 VS = ±8V, RL = 300Ω, AV = 50, (Note 3) ±6.4 ± 6.6 GE Gain Error IS Supply Current IS/D VO = ±1V, AV = 10, RL = 1k Shutdown Supply Current Pin 5 at V –, (Note 11) Shutdown Pin Current Pin 5 at V – 1.0 6.0 % 13 17 mA 0.8 1.5 mA 5 25 µA 3 LT1189 + – 5V ELECTRICAL CHARACTERISTICS 0°C ≤ TA ≤ 70°C, (Note 3) V = ±5V, V = 0V, R = 900Ω from pins 6 to 8, R = 100Ω from pin 8 to ground, R = R S REF FB1 FB2 SYMBOL PARAMETER CONDITIONS VOS Input Offset Voltage (Note 4) Either Input SOIC Package ∆VOS /∆T Input VOS Drift IOS Input Offset Current Either Input IB Input Bias Current Either Input L Common-Mode Rejection Ratio + RFB2 = 1k, CL ≤ 10pF, pin 5 open. MIN LT1189C TYP MAX 1.0 1.0 3.0 6.0 80 mV mV 0.2 1.5 µA ± 0.5 ±3.5 µA 3.5 V –2.5 VCM = – 2.5V to 3.5V UNITS µV/°C 5.0 Input Voltage Range CMRR FB1 105 dB PSRR Power Supply Rejection Ratio VS = ±2.375V to ±8V 70 90 dB VOUT Output Voltage Swing VS = ±5V, RL = 1k, AV = 50 ±3.7 ±4.0 V VS = ±8V, RL = 1k, AV = 50 ±6.6 ±7.0 VS = ±8V, RL = 300Ω, AV = 50, (Note 3) ±6.4 ± 6.6 VO = ±1V, AV = 10, RL = 1k 1.0 13 17 mA Shutdown Supply Current Pin 5 at V –, (Note 11) 0.8 1.5 mA Shutdown Pin Current Pin 5 at V – 5 25 µA GE Gain Error IS Supply Current IS/D 3.5 % CHARACTERISTICS 5V ELECTRICAL + – 0°C ≤ TA ≤ 70°C, (Note 3) VS = +5V, VS = 0V, VREF = 2.5V, RFB1 = 900Ω from pins 6 to 8, RFB2 = 100Ω from pin 8 to VREF, RL = RFB1 + RFB2 = 1k, CL ≤ 10pF, pin 5 open. MIN LT1189C TYP MAX SYMBOL PARAMETER CONDITIONS VOS Input Offset Voltage, (Note 4) Either Input ∆VOS /∆T Input VOS Drift IOS Input Offset Current Either Input 0.2 1.5 µA IB Input Bias Current Either Input ± 0.5 ± 3.5 µA 3.5 V 1.0 2.0 CMRR Common-Mode Rejection Ratio VCM = 2.0V to 3.5V VOUT Output Voltage Swing RL = 300Ω to Ground VOUT High (Note 3) VOUT Low IS/D Supply Current Shutdown Supply Current Pin 5 at V, (Note 11) Shutdown Pin Current Pin 5 at V – Note 1: A heat sink may be required to keep the junction temperature below absolute maximum when the output is shorted continuously. Note 2: TJ is calculated from the ambient temperature T A and power dissipation PD according to the following formulas: LT1189MJ8, LT1189CJ8: TJ = TA + (PD × 100°C/W) LT1189CN8: TJ = TA + (PD × 100°C/W) LT1189CS8: TJ = TA + (PD × 150°C/W) Note 3: When RL = 1k is specified, the load resistor is RFB1 + RFB2, but when RL = 300Ω is specified, then an additional 430Ω is added to the output such that (RFB1 + RFB2) in parallel with 430Ω is RL = 300Ω. Note 4: VOS measured at the output (pin 6) is the contribution from both input pair, and is input referred. Note 5: VIN LIM is the maximum voltage between –V IN and +VIN (pin 2 and pin 3) for which the output can respond. 4 UNITS mV µV/°C 5.0 Input Voltage Range IS 3.0 80 100 dB 3.5 4.0 V 0.15 0.4 12 16 mA 0.8 1.5 mA 5 25 µA Note 6: Slew rate is measured between ±1V on the output, with a VIN step of ±0.5V, AV = 10 and RL = 1k. Note 7: Full power bandwidth is calculated from the slew rate measurement: FPBW = SR/2πVp. Note 8: Settling time measurement techniques are shown in “Take the Guesswork Out of Settling Time Measurements,” EDN, September 19, 1985. Note 9: NTSC (3.58MHz). Note 10: AC parameters are 100% tested on the ceramic and plastic DIP packaged parts (J8 and N8 suffix) and are sample tested on every lot of the SO packaged parts (S8 suffix). Note 11: See Application section for shutdown at elevated temperatures. Do not operate shutdown above T J > 125°C. LT1189 U W TYPICAL PERFOR A CE CHARACTERISTICS Input Bias Current vs Common-Mode Voltage V+ 100 3.0 VS = ±5V VS = ±5V 2.0 1.5 –55°C 1.0 25°C 0.5 0 +IB 0 –100 –IB IOS –200 –300 125°C – 5 – 4 –3 –2 –1 0 1 2 3 COMMON-MODE VOLTAGE (V) 4 –400 –50 5 –25 0 25 75 50 TEMPERATURE (°C) V S = ±5V T A = 25°C RS = 0Ω 140 120 100 80 60 40 20 0 1k 10k FREQUENCY (Hz) 100 8 6 4 0 125°C 10 1k 10k FREQUENCY (Hz) GAIN ERROR (%) 1.0 4 6 8 ±SUPPLY VOLTAGE (V) 10 LT1189 • TPC06 Open-Loop Gain vs Temperature 16 VS = ±5V VOUT = ±1V AV = 10 RL = 1k 14 OPEN-LOOP GAIN (kV/V) –1.4 VS/D = –VEE + 0.2V 2 0 100k Gain Error vs Temperature VS = ±5V 2.0 12 8 100 –1.2 3.0 25°C 2 Shutdown Supply Current vs Temperature VS/D = –VEE + 0.4V –55°C 14 LT1189 • TPC05 5.0 125 Supply Current vs Supply Voltage VS = ±5V TA = 25°C RS = 100k 10 6.0 100 16 10 100k VS/D = –VEE + 0.6V 0 25 50 75 TEMPERATURE (°C) LT1189 • TPC03 12 LT1189 • TPC04 4.0 V + = –1.8V TO –9V 1.0 V– – 50 –25 125 SUPPLY CURRENT (mA) 200 100 2.0 1.5 Equivalent Input Noise Current vs Frequency EQUIVALENT INPUT NOISE CURRENT (pA/√Hz) EQUIVALENT INPUT NOISE VOLTAGE (nV/√Hz) Equivalent Input Noise Voltage vs Frequency 10 –2.0 LT1189 • TPC02 LT1189 • TPC01 160 –1.0 –1.5 0.5 – 0.5 180 V + = 1.8V TO 9V –0.5 COMMON-MODE RANGE (V) INPUT BIAS CURRENT (nA) INPUT BIAS CURRENT (µA) 2.5 SHUTDOWN SUPPLY CURRENT (mA) Common-Mode Voltage vs Temperature Input Bias Current vs Temperature –1.6 –1.8 –2.0 –2.2 VS = ±5V VO = ±3V RL = 1k 12 10 RL = 500Ω 8 6 4 2 VS/D = –VEE 0 –50 –25 0 25 75 50 TEMPERATURE (°C) 100 125 LT1189 • TPC07 –2.4 –50 –25 0 25 50 75 TEMPERATURE (°C) 100 125 LT1189 • TPC08 0 –50 –25 25 75 0 50 TEMPERATURE (°C) 100 125 LT1189 • TPC09 5 LT1189 U W TYPICAL PERFOR A CE CHARACTERISTICS Open-Loop Voltage Gain vs Load Resistance Gain, Phase vs Frequency 100 80 GAIN 40 40 20 20 0 0 PHASE MARGIN (DEG) 60 60 –20 –20 100k 1M 10M FREQUENCY (Hz) 250 30 20 10 1k LOAD RESISTANCE (Ω) LT1189 • TPC11 85 25 75 0 50 TEMPERATURE (°C) 10 1 0.1 55 125 100 1k 10k 100k 1M FREQUENCY (Hz) +PSRR –PSRR 20 0 –20 1k 10k 1M 100k FREQUENCY (Hz) 10M 100M LT1189 • TPC16 50 40 V+ – 0.7 VS = ±5V OUTPUT SATURATION VOLTAGE (V) 40 OUTPUT SHORT CIRCUIT CURRENT (mA) POWER SUPPLY REJECTION RATIO (dB) 60 60 1M 10M FREQUENCY (Hz) 35 34 33 32 31 30 –50 –25 50 0 25 75 TEMPERATURE (°C) 100 125 LT1189 • TPC17 100M LT1189 • TPC15 36 VS = ±5V TA = 25°C VRIPPLE = ±300mV 70 30 100k 100M Output Short Circuit Current vs Temperature 80 6 10M VS = ±5V TA = 25°C RL = 1k 80 LT1189 • TPC14 LT1189 • TPC13 Power Supply Rejection Ratio vs Frequency 10 90 COMMON-MODE REJECTION RATIO (dB) OUTPUT IMPEDANCE (Ω ) GAIN BANDWIDTH PRODUCT (MHz) 65 PHASE MARGIN –25 4 8 6 ±SUPPLY VOLTAGE (V) LT1189 • TPC12 100 PHASE MARGIN (DEG) 75 150 2 Common-Mode Rejection Ratio vs Frequency VS = ±5V TA = 25°C AV = 10 GAIN BANDWIDTH PRODUCT 100 –50 0 10k Output Impedance vs Frequency VS = ±5V R L = 1k AV = 20dB 200 TA = 125°C 150 LT1189• TPC10 Gain Bandwidth Product and Phase Margin vs Temperature 250 TA = 25°C 200 100 0 100 100M TA = –55°C AV = 20dB VS = ±5V VO = ±3V TA = 25°C GAIN BANDWIDTH PRODUCT (MHz) PHASE 80 VOLTAGE GAIN (dB) VS = ±5V TA = 25°C RL = 1k OPEN-LOOP VOLTAGE GAIN (kV/V) 100 Gain Bandwidth Product vs Supply Voltage ± Output Swing vs Supply Voltage –0.8 125°C –0.9 25°C –1.0 –55°C –1.1 0.5 RL = 1k ±1.8V ≤ VS ≤ ±9V 0.4 125°C 25°C 0.3 –55°C 0.2 0.1 V– 0 2 4 6 8 ±SUPPLY VOLTAGE (V) 10 LT1189 • TPC18 LT1189 U W TYPICAL PERFOR A CE CHARACTERISTICS Output Voltage Swing vs Load Resistance Slew Rate vs Temperature 5 300 VS = ±5V TA = –55°C TA = 25°C SLEW RATE (V/µs) OUTPUT VOLTAGE SWING (V) –SLEW RATE 3 TA = 25°C 1 TA = –55°C –1 TA = 25°C –3 TA = 25°C VS = ±5V RL = 1k VO = ±2V AV = 10 –5 10 100 LOAD RESISTANCE (Ω) +SLEW RATE 250 200 –50 –25 1000 0 25 50 75 TEMPERATURE (°C) 100 LT1189 • TPC19 LT1189 • TPC20 Harmonic Distortion vs Output Level Output Voltage Step vs Settling Time, AV = 10 0 VS = ±5V TA = 25°C RL = 1k 10mV 0 10mV –2 VS = ±5V TA = 25°C RL = 1k f = 10MHz AV = 10 –10 DISTORTION (dBc) OUTPUT VOLTAGE STEP (V) 4 2 125 –20 HD3 –30 HD2 –40 –50 –4 100 –60 140 180 220 260 SETTLING TIME (ns) 300 340 0 3 1 2 OUTPUT VOLTAGE (VP-P) LT1189 • TPC22 LT1189 • TPC21 Large-Signal Transient Reponse 4 Small-Signal Transient Reponse AV = 10, RL = 1k, +SR = 223V/µs, –SR = 232V/µs AV = 10, RL = 1k, tr = 9.40ns LT1189 • TPC23 LT1189 • TPC24 7 LT1189 W U U UO APPLICATI S I FOR ATIO The primary use of the LT1189 is in converting high speed differential signals to a single-ended output. The LT1189 video difference amplifier has two uncommitted high input impedance (+) and (–) inputs. The amplifier has another set of inputs which can be used for reference and feedback. Additionally, this set of inputs give gain adjust, and DC control to the differential amplifier. The voltage gain of the LT1189 is set like a conventional operational amplifier. Feedback is applied to pin 8, and it is optimized for gains of 10 or greater. The amplifier can be operated singleended by connecting either the (+) or (–) inputs to the +/REF (pin 1). The voltage gain is set by the resistors: (RFB + RG)/RG. Like the single-ended case, the differential voltage gain is set by the external resistors: (RFB + RG)/RG. The maximum input differential signal for which the output will respond is approximately ±170mV. S/D 5 VIN S/D V+ 3 7 + 2 – LT1189 1 +/REF 8 –/FB 4 6 V+ 5 3 7 + 2 – LT1189 1 +/REF 8 –/FB 4 V IN VOUT V– RFB RG AV = + 6 VOUT RG RG AV = – The LT1189 is quite tolerant of power supply bypassing. In some applications a 0.1µF ceramic disc capacitor placed 1/2 inch from the amplifier is all that is required. In applications requiring good settling time, it is important to use multiple bypass capacitors. A 0.1µF ceramic disc in parallel with a 4.7µF tantalum is recommended. Calculating the Output Offset Voltage Both input stages contribute to the output offset voltage at pin 6. The feedback correction forces balance in the input stages by introducing an Input VOS at pin 8. The complete expression for the output offset voltage is: VOUT = (VOS + IOS(RS) + IB(RREF)) × (RFB + RG)/RG + IB(RFB) RS represents the input source resistance, typically 75Ω, and RREF represents finite source impedance from the DC reference voltage, for VREF grounded, RREF = 0Ω the IOS is normally a small contributor and the expression simplifies to: VOUT = VOS(RFB + RG)/RG + IB(RFB) If RFB is limited to 1k, the last term of the equation contributes only 2mV since IB is less than 2µA. V– RFB RFB + RG Power Supply Bypassing RFB + RG 7 V+ RG 6 S/D VIN DIFF VIN S/D V+ 5 3 7 + 2 – LT1189 1 +/REF 8 –/FB 4 6 V+ 5 3 7 + 2 – LT1189 1 +/REF 8 –/FB 4 VIN DIFF VOUT V IN RG V– RFB RFB 6 Q1 VOUT 3 V– RFB + RS 2 – RS Q2 RE 300 345µA RG VO = (VIN DIFF + VIN) RFB + RG RG VO = ( RFB + RG RG (V IN DIFF – RFB ( R (V G IN Q3 + 1 REF RREF Q4 8 RG RE 300 350µA 4 V– LT1189 • AI01 Figure 1. Simplified Input Stage Schematic 8 LT1189 • AI02 LT1189 W U U UO APPLICATI S I FOR ATIO High Voltage Instrumentation Amplifier Response Instrumentation Amplifier Rejects High Voltage 20 Instrumentation amplifiers are often used to process slowly varying outputs from transducers. With the LT1189 it is easy to make an instrumentation amplifier that can respond to rapidly varying signals. Attenuation resistors in front of the LT1189 allow very large common-mode signals to be rejected while maintaining good frequency response. The input common-mode and differential-mode signals are reduced by 100:1, while the closed-loop gain is set to be 100, thereby maintaining unity-gain input to output. The unique topology allows for frequency response boost by adding 150pF to pin 8 as shown. VOLTAGE GAIN (dB) 0 DIFFERENTIAL-MODE RESPONSE –20 –40 – 60 100k COMMON-MODE RESPONSE 1M 10M FREQUENCY (Hz) 100M LT1189 • AI05 3.5MHz Instrumentation Amplifier Rejects 120VP-P 10k* VIN 5V 100* 2 1 10k* VCM 120VP-P 3 8 100* 7 – FB LT1189 6 4 –5V 10k 150pF * 0.1% RESISTORS WORST CASE CMRR = 48dB + REF 100Ω Operating with Low Closed-Loop Gain The LT1189 has been optimized for closed-loop gains of 10 or greater. The amplifier can be operated at much lower closed-loop gains with the aid of a capacitor CFB across the feedback resistor, (feedback zero). This capacitor lowers the closed-loop 3dB bandwidth. The bandwidth cannot be made arbitrarily low because CFB is a short at high frequency and the amplifier will appear configured unity-gain. As an approximate guideline, make BW × AVCL = 200MHz. This expression expands to: LT1189 • AI03 Output of Instrumentation Amplifier with 1MHz Square Wave Riding on 120VP-P at the Input A VCL = 200MHz 2π(RFB )(C FB ) or: C FB = A VCL (200MHz)(2π)(RFB ) The effect of the feedback zero on the transient and frequency response is shown for AV = 4. LT1189 • AI04 9 LT1189 W U U UO APPLICATI S I FOR ATIO Closed-Loop Voltage Gain vs Frequency CLOSED-LOOP VOLTAGE GAIN (dB) 30 Although it is possible to reduce the closed-loop bandwidth by using a feedback zero, instability can occur if the bandwidth is made too low. An alternate technique is to do differential filtering at the input of the amplifier. This technique filters the differential input signal, and the differential noise, but does not filter common-mode noise. Common-mode noise is rejected by the LT1189’s CMRR. CFB = 0pF 20 10 CFB = 5pF 0 –10 –20 100k VS = ±5V TA = 25°C AV = 4 RFB = 900Ω RG = 300Ω 1M 10M FREQUENCY (Hz) Reducing the Closed-Loop Bandwidth 10MHz Bandwidth Limited Amplifier 100M R1 110Ω LT1189 • AI06 SIG Small-Signal Transient Response eND eNCM 5V 3 2 C1 68pF 1 8 + 7 – LT1189 6 REF 4 FB –5V R2 110Ω VOUT 909Ω AV = 10 100Ω f –3dB = 1 2π(R1 + R2)C1 VOUT = SIG + eND eNCM + CMR FILTER LT1189 • AI09 Using the Shutdown Feature AV = 4, RFB = 910Ω, RG = 300Ω LT1189 • AI07 Small-Signal Transient Response AV = 4, RFB = 910Ω, RG = 300Ω, CFB = 5pF LT1189 • AI08 10 The LT1189 has a unique feature that allows the amplifier to be shutdown for conserving power, or for multiplexing several amplifiers onto a common cable. The amplifier will shutdown by taking pin 5 to V –. In shutdown, the amplifier dissipates 15mW while maintaining a true high impedance output state of about 20kΩ in parallel with the feedback resistors. For MUX applications, the amplifiers may be configured inverting, non-inverting, or differential. When the output is loaded with as little as 1kΩ from the amplifier’s feedback resistors, the amplifier shuts off in 600ns. This shutoff can be under the control of HC CMOS operating between 0V and – 5V. LT1189 W U U UO APPLICATI S I FOR ATIO 1MHz Sine Wave Gated Off with Shutdown Pin The ability to maintain shutoff is shown on the curve Shut down Supply Current vs Temperature in the Typical Performance Characteristics section. At very high elevated temperature it is important to hold the shutdown pin close to the negative supply to keep the supply current from increasing. SHUTDOWN VOUT AV = 10, RFB = 900Ω, RG = 100Ω LT1189 • AI10 UO TYPICAL APPLICATI Differential Receiver MUX for Power Down Applications 15k 1.5k CABLE 1 3 2 15k VDC 1 REF 8 FB 1.5k CMOS IN CHANNEL SELECT 5V + – 7 LT1189 6 4 5 1k –5V 100Ω 1k 74HC04 74HC04 VOUT 1k –5V 15k CABLE 2 1.5k 15k 1.5k 3 + 2 – VDC 1 REF 8 FB 5V 5 7 LT1189 4 –5V 1k 100Ω 6 1% RESISTORS WORST CASE CMRR = 28dB TYPICALLY 35dB LT1189 • TA03 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. 11 LT1189 W W SI PLIFIED SCHE ATIC 7 V+ VBIAS VBIAS CM + 3 C FF – 2 +V 6 VOUT +V * 4 V– 5 S/D 1 +/REF 8 –/FB * SUBSTRATE DIODE, DO NOT FORWARD BIAS LT1189 • SS U PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted. 0.290 – 0.320 (7.366 – 8.128) J8 Package 8-Lead Hermetic DIP 0.200 (5.080) MAX CORNER LEADS OPTION (4 PLCS) 0.015 – 0.060 (0.381 – 1.524) 0.023 – 0.045 (0.58 – 1.14) HALF LEAD OPTION 0.008 – 0.018 (0.203 – 0.460) 0° – 15° 0.385 ± 0.025 (9.779 ± 0.635) 0.045 – 0.065 (1.14 – 1.65) FULL LEAD OPTION 0.300 – 0.320 (7.620 – 8.128) 0.045 – 0.065 (1.143 – 1.651) 8 6 7 5 0.025 (0.635) RAD TYP 0.220 – 0.310 (5.588 – 7.874) 2 3 4 0.125 3.175 0.100 ± 0.010 MIN (2.540 ± 0.254) 0.400 (10.160) MAX 0.130 ± 0.005 (3.302 ± 0.127) 8 7 6 5 0.065 (1.651) TYP 0.009 – 0.015 (0.229 – 0.381) ( 0.405 (10.287) MAX 1 0.045 – 0.065 (1.14 – 1.65) 0.014 – 0.026 (0.360 – 0.660) N8 Package 8-Lead Plastic DIP 0.005 (0.127) MIN +0.025 0.325 –0.015 +0.635 8.255 –0.381 0.250 ± 0.010 (6.350 ± 0.254) 0.125 (3.175) MIN 0.045 ± 0.015 (1.143 ± 0.381) ) 0.100 ± 0.010 (2.540 ± 0.254) 0.020 (0.508) MIN 1 2 4 3 0.018 ± 0.003 (0.457 ± 0.076) 0.189 – 0.197 (4.801 – 5.004) 0.010 – 0.020 × 45° (0.254 – 0.508) 0°– 8° TYP 0.016 – 0.050 0.406 – 1.270 0.014 – 0.019 (0.355 – 0.483) 0.050 (1.270) BSC 12 6 5 0.228 – 0.244 (5.791 – 6.197) 0.150 – 0.157 (3.810 – 3.988) 1 Linear Technology Corporation 7 0.004 – 0.010 (0.101 – 0.254) 0.008 – 0.010 (0.203 – 0.254) S8 Package 8-Lead Plastic SOIC 8 0.053 – 0.069 (1.346 – 1.752) 2 3 4 BA/LT/GP 0293 10K REV 0 1630 McCarthy Blvd., Milpitas, CA 95035-7487 (408) 432-1900 ● FAX: (408) 434-0507 ● TELEX: 499-3977 LINEAR TECHNOLOGY CORPORATION 1993