LT1227 140MHz Video Current Feedback Amplifier U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ 140MHz Bandwidth: AV = 2, RL = 150Ω 1100V/µs Slew Rate Low Cost 30mA Output Drive Current 0.01% Differential Gain 0.01° Differential Phase High Input Impedance: 14MΩ, 3pF Wide Supply Range: ±2V to ±15V Shutdown Mode: IS < 250µA Low Supply Current: IS = 10mA Inputs Common Mode to Within 1.5V of Supplies Outputs Swing Within 0.8V of Supplies ■ ■ ■ ■ S Video Amplifiers Cable Drivers RGB Amplifiers Test Equipment Amplifiers 50Ω Buffers for Driving Mixers The LT1227 is manufactured on Linear Technology’s proprietary complementary bipolar process. UO ■ A shutdown feature switches the device into a high impedance, low current mode, allowing multiple devices to be connected in parallel and selected. Input to output isolation in shutdown is 70dB at 10MHz for input amplitudes up to 10VP-P. The shutdown pin interfaces to open collector or open drain logic and takes only 4µs to enable or disable. The LT1227 comes in the industry standard pinout and can upgrade the performance of many older products. For a dual or quad version, see the LT1229/1230 data sheet. UO APPLICATI The LT1227 is a current feedback amplifier with wide bandwidth and excellent video characteristics. The low differential gain and phase, wide bandwidth, and 30mA output drive current make the LT1227 well suited to drive cables in video systems. TYPICAL APPLICATI Video Cable Driver Differential Gain and Phase vs Supply Voltage 0.20 + 75Ω LT1227 75Ω CABLE RF 1k VOUT VOUT =1 VIN 75Ω 0.16 0.16 0.12 0.12 0.08 0.08 ∆φ DIFFERENTIAL GAIN (%) – RG 1k 0.20 NTSC COMPOSITE f = 3.58MHz DIFFERENTIAL PHASE (DEG) VIN 0.04 0.04 1227 TA01 ∆G 0 5 7 11 13 9 SUPPLY VOLTAGE (±V) 15 0 LT1227 • TA02 1 LT1227 U U RATI GS W W W W AXI U U ABSOLUTE PACKAGE/ORDER I FOR ATIO Supply Voltage ..................................................... ±18V Input Current ...................................................... ±15mA Output Short Circuit Duration (Note 1) ........ Continuous Operating Temperature Range LT1227C .................................................. 0°C to 70°C LT1227M ......................................... – 55°C to 125°C Storage Temperature Range ................. – 65°C to 150°C Junction Temperature Plastic Package ................................................ 150°C Ceramic Package ............................................. 175°C Lead Temperature (Soldering, 10 sec.)................ 300°C ORDER PART NUMBER TOP VIEW NULL 1 8 SHUTDOWN –IN 2 7 V+ +IN 3 6 OUT V – LT1227MJ8 LT1227CN8 5 NULL 4 N8 PACKAGE J8 PACKAGE 8-LEAD CERAMIC DIP 8-LEAD PLASTIC DIP TJMAX = 175°C, θJA = 100°C/W (J) TJMAX = 150°C, θJA = 100°C/W (N) TOP VIEW LT1227CS8 NULL 1 8 SHUTDOWN –IN 2 7 V+ +IN 3 6 V– 4 S8 PART MARKING OUT 1227 5 NULL S8 PACKAGE 8-LEAD PLASTIC SO TJMAX = 150°C, θJA = 150°C/W Consult factory for Industrial grade parts. ELECTRICAL CHARACTERISTICS SYMBOL VOS PARAMETER Input Offset Voltage IIN+ Input Offset Voltage Drift Noninverting Input Current VCM = 0, ±5V ≤ VS ≤ ±15V, pulse tested, unless otherwise noted. CONDITIONS TA = 25°C MIN TYP ±3 ● 10 ±0.3 ● TA = 25°C ● IIN– Inverting Input Current ±10 TA = 25°C ● en +in –in RIN Input Noise Voltage Density Noninverting Input Noise Current Density Inverting Input Noise Current Density Input Resistance CIN Input Capacitance Input Voltage Range f = 1kHz, RF = 1k, RG = 10Ω, RS = 0Ω f = 1kHz f = 1kHz VIN = ±13V, VS = ±15V VIN = ±3V, VS = ±5V ● ● VS = ±15V, TA = 25°C ● VS = ±5V, TA = 25°C ● CMRR Common-Mode Rejection Ratio Inverting Input Current Common-Mode Rejection 2 VS = ±15V, VCM = ±13V, TA = 25°C VS = ±15V, VCM = ±12V VS = ±5V, VCM = ±3V, TA = 25°C VS = ±5V, VCM = ±2V VS = ±15V, VCM = ±13V, TA = 25°C VS = ±15V, VCM = ±12V VS = ±5V, VCM = ±3V, TA = 25°C VS = ±5V, VCM = ±2V ● ● 1.5 1.5 ±13 ±12 ±3 ±2 55 55 55 55 ±3 ±10 ±60 ±100 3.2 1.7 32 14 11 3 ±13.5 ±3.5 62 61 3.5 ● 4.5 ● MAX ±10 ±15 10 10 10 10 UNITS mV mV µV/°C µA µA µA µA nV/√Hz pA/√Hz pA/√Hz MΩ MΩ pF V V V V dB dB dB dB µA/V µA/V µA/V µA/V LT1227 ELECTRICAL CHARACTERISTICS SYMBOL PSRR PARAMETER Power Supply Rejection Ratio AV Noninverting Input Current Power Supply Rejection Inverting Input Current Power Supply Rejection Large-Signal Voltage Gain ROL Transresistance, ∆VOUT/∆IIN– VOUT Maximum Output Voltage Swing VCM = 0, ±5V ≤ VS ≤ ±15V, pulse tested, unless otherwise noted. CONDITIONS VS = ±2V to ±15V, TA = 25°C VS = ±3V to ±15V VS = ±2V to ±15V, TA = 25°C VS = ±3V to ±15V VS = ±2V to ±15V, TA = 25°C VS = ±3V to ±15V VS = ±15V, VOUT = ±10V, RL = 1k VS = ±5V, VOUT = ±2V, RL = 150Ω VS = ±15V, VOUT = ±10V, RL = 1k VS = ±5V, VOUT = ±2V, RL = 150Ω VS = ±15V, RL = 400Ω, TA = 25°C ● MAX 2 50 50 5 5 0.25 ● ● ● ● ● ● ● Maximum Output Current Supply Current (Note 2) TYP 80 ● VS = ±5V, RL = 150Ω, TA = 25°C IOUT IS MIN 60 60 RL = 0Ω, TA = 25°C VS = ±15V, VOUT = 0V, TA = 25°C 55 55 100 100 ±12 ±10 ±3 ±2.5 30 72 72 270 240 ±13.5 ±3.7 60 10 ● Positive Supply Current, Shutdown VS = ±15V, Pin 8 Voltage = 0V, TA = 25°C 120 ● I8 SR tr, tf BW tr, tf tS Shutdown Pin Current (Note 3) Output Leakage Current, Shutdown Slew Rate (Notes 4 and 5) Rise and Fall Time, VOUT = 1VP-P Small-Signal Bandwidth Small-Signal Rise and Fall Time Propagation Delay Small-Signal Overshoot Settling Time Differential Gain (Note 6) Differential Phase (Note 6) VS = ±15V VS = ±15V, Pin 8 Voltage = 0V, TA = 25°C TA = 25°C VS = ±5V, RF = 1k, RG = 1k, RL = 150Ω VS = ±15V, RF = 1k, RG = 1k, RL = 150Ω VS = ±15V, RF = 1k, RG = 1k, RL = 100Ω VS = ±15V, RF = 1k, RG = 1k, RL = 100Ω VS = ±15V, RF = 1k, RG = 1k, RL = 100Ω 0.1%, VOUT = 10V, RF = 1k, RG = 1k, RL = 1k VS = ±15V, RF = 1k, RG = 1k, RL = 150Ω VS = ±15V, RF = 1k, RG = 1k, RL = 1k VS = ±15V, RF = 1k, RG = 1k, RL = 150Ω VS = ±15V, RF = 1k, RG = 1k, RL = 1k The ● denotes specifications which apply over the operating temperature range. Note 1: A heat sink may be required depending on the power supply voltage. Note 2: The supply current of the LT1227 has a negative temperature coefficient. For more information, see Typical Performance Characteristics curves. Note 3: Ramp pin 8 voltage down from 15V while measuring IS. When IS drops to less than 0.5mA, measure pin 8 current. ● 500 1100 8.7 140 3.3 3.4 5 50 0.014 0.010 0.010 0.013 15.0 17.5 300 500 300 10 UNITS dB dB nA/V nA/V µA/V µA/V dB dB kΩ kΩ V V V V mA mA mA µA µA µA µA V/µs ns MHz ns ns % ns % % DEG DEG Note 4: Slew rate is measured at ±5V on a ±10V output signal while operating on ±15V supplies with RF = 2k, RG = 220Ω and R L = 400Ω. Note 5: AC parameters are 100% tested on the ceramic and plastic DIP package parts (J and N suffix) and are sample tested on every lot of the SO packaged parts (S suffix). Note 6: NTSC composite video with an output level of 2V. 3 LT1227 U W TYPICAL PERFOR A CE CHARACTERISTICS Voltage Gain and Phase vs Frequency, Gain = 6dB 135 225 4 3 VS = ±15V RL = 100Ω RF = 910Ω 1 0 0.1 RF = 750Ω 100 RF = 1k 80 60 40 RF = 2k 20 0 1 10 FREQUENCY (MHz) 0 100 2 4 6 8 10 12 14 SUPPLY VOLTAGE (±V) LT1227 • TPC01 90 21 135 20 180 GAIN 225 18 17 16 VS = ±15V RL = 100Ω RF = 825Ω 15 14 0.1 120 100 RF = 250Ω RF = 500Ω 80 RF = 750Ω 60 RF = 1k 40 RF = 2k 41 135 40 180 225 37 35 34 0.1 VS = ±15V RL = 100Ω RF = 500Ω 2 4 6 8 10 12 14 SUPPLY VOLTAGE (±V) 16 100 18 RF = 500Ω 100 80 RF = 750Ω 60 RF = 1k 40 RF = 2k 0 18 2 4 6 8 10 12 14 SUPPLY VOLTAGE (±V) 18 16 16 14 14 RF = 500Ω RF = 1k 10 RF = 2k 8 18 LT1227 • TPC06 18 12 16 –3dB Bandwidth vs Supply Voltage, Gain = 100, RL = 1k 6 4 RF = 500Ω 12 RF = 1k RF = 2k 10 8 6 4 2 0 0 1 10 FREQUENCY (MHz) 120 20 2 LT1227 • TPC07 4 –3dB BANDWIDTH (MHz) VOLTAGE GAIN (dB) 90 PHASE SHIFT (DEG) 42 16 PEAKING ≤ 0.5dB PEAKING ≤ 5dB LT1227 • TPC05 0 38 6 8 10 12 14 SUPPLY VOLTAGE (±V) 0 0 45 GAIN 4 140 –3dB Bandwidth vs Supply Voltage, Gain = 100, RL = 100Ω PHASE 2 LT1227 • TPC03 0 100 44 36 0 –3dB Bandwidth vs Supply Voltage, Gain = 10, RL = 1k 140 Voltage Gain and Phase vs Frequency, Gain = 40dB 39 0 180 LT1227 • TPC04 43 40 160 20 1 10 FREQUENCY (MHz) RF = 1k 60 18 PEAKING ≤ 0.5dB PEAKING ≤ 5dB 160 –3dB BANDWIDTH (MHz) VOLTAGE GAIN (dB) 45 22 19 16 180 0 PHASE SHIFT (DEG) 23 RF = 1.5k 80 –3dB Bandwidth vs Supply Voltage, Gain = 10, RL = 100Ω PHASE RF = 2k 100 LT1227 • TPC02 Voltage Gain and Phase vs Frequency, Gain = 20dB 24 RF = 750Ω 140 120 20 –3dB BANDWIDTH (MHz) 2 RF = 500Ω –3dB BANDWIDTH (MHz) 5 180 GAIN 140 120 PEAKING ≤ 0.5dB PEAKING ≤ 5dB 160 –3dB BANDWIDTH (MHz) 90 7 180 PEAKING ≤ 0.5dB PEAKING ≤ 5dB 160 –3dB BANDWIDTH (MHz) VOLTAGE GAIN (dB) 45 PHASE SHIFT (DEG) PHASE 8 6 180 0 10 9 –3dB Bandwidth vs Supply Voltage, Gain = 2, RL = 1k –3dB Bandwidth vs Supply Voltage, Gain = 2, RL = 100Ω 0 2 4 6 8 10 12 14 SUPPLY VOLTAGE (±V) 16 18 LT1227 • TPC08 0 2 4 6 8 10 12 14 SUPPLY VOLTAGE (±V) 16 18 LT1227 • TPC09 LT1227 U W TYPICAL PERFOR A CE CHARACTERISTICS Maximum Capacitive Load vs Feedback Resistor Total Harmonic Distortion vs Frequency 0.1 VS = ±5V VS = ±15V 100 10 1 2 FEEDBACK RESISTOR (kΩ) VO = 7VRMS 3 1k 10k FREQUENCY (Hz) V+ OUTPUT SATURATION VOLTAGE (V) –1.5 –2.0 2.0 1.5 V – = –2V TO –18V 0.5 V– –50 –25 50 25 0 75 TEMPERATURE (°C) 100 –0.5 1.0 0.5 50 25 75 0 TEMPERATURE (°C) LT1227 • TPC13 10 en +in 1k 10k FREQUENCY (Hz) 40 30 –50 –25 125 100k LT1227 • TPC16 0 25 50 75 100 125 150 175 TEMPERATURE (°C) LT1227 • TPC15 Output Impedance vs Frequency 100 80 100 50 Power Supply Rejection vs Frequency POWER SUPPLY REJECTION (dB) SPOT NOISE (nV/√Hz OR pA/√Hz) 100 60 LT1227 • TPC14 100 1 10 LT1127 • TPC12 70 –1.0 Spot Noise Voltage and Current vs Frequency VS = ±15V VS = ±15V RL = 100Ω RF = RG = 1k 60 POSITIVE NEGATIVE 40 20 0 10k 100 Output Short-Circuit Current vs Junction Temperature RL = ∞ ±2V ≤ VS ≤ ±18V V– –50 –25 125 –in 10 FREQUENCY (MHz) 1 OUTPUT SHORT-CIRCUIT CURRENT (mA) V+ 1.0 100k Output Saturation Voltage vs Temperature V + = 2V TO 18V AV = +2 LT1227 • TPC11 Input Common Mode Limit vs Temperature –1.0 AV = +1 10 0 100 LT1227 • TPC10 –0.5 AV = +10 AV = –1 15 5 VO = 1VRMS 0.001 10 1 0 0.01 VS = ±15V RL = 1k RF = 1k 20 10 OUTPUT IMPEDANCE (Ω) CAPACITIVE LOAD (pF) 1000 25 VS = ±15V RL = 400Ω RF = RG = 1k OUTPUT VOLTAGE (VP-P) RL = 1k PEAKING ≤ 5dB GAIN = 2 TOTAL HARMONIC DISTORTION (%) 10000 COMMON MODE RANGE (V) Maximum Undistorted Output vs Frequency 1 RF = RG = 2k RF = RG = 1k 0.1 0.01 100k 1M 10M FREQUENCY (Hz) 100M LT1227 • TPC17 0.001 10k 100k 1M 10M FREQUENCY (Hz) 100M LT1227 • TPC18 5 LT1227 U W TYPICAL PERFOR A CE CHARACTERISTICS Settling Time to 1mV vs Output Step Settling Time to 10mV vs Output Step 6 4 4 OUTPUT STEP (V) 6 NONINVERTING 2 INVERTING 0 –2 –4 VS = ±15V RF = RG = 1k 8 13 12 2 NONINVERTING 0 INVERTING –2 –4 8 –8 5 –10 60 40 SETTLING TIME (ns) 80 100 4 4 0 12 16 8 SETTLING TIME (µs) 1M 10M FREQUENCY (Hz) 6 8 10 12 14 SUPPLY VOLTAGE (±V) 0.01 DIFFERENTIAL GAIN (%) DIFFERENTIAL PHASE (DEG) 0.10 0.15 0.20 VS = ±15V AV = 2 RL = 1k RF = 1k RG = 1k 0.02 0.04 0.05 1M 10M 100M (VO)DC = 0.5V 1.0V 2.0V 0.03 VS = ±15V AV = 2 RL = 1k RF = 1k RG = 1k 0.06 100k 1M FREQUENCY (Hz) LT1227 • TPC22 10M 100M FREQUENCY (Hz) LT1227 • TPC23 2nd and 3rd Harmonic Distortion vs Frequency 18 Differential Gain vs Frequency (VO)DC = 0.5V 1.0V 1.5V 2.0V 0.05 0.30 100k 100M 16 0 0.25 0.1 100k 4 LT1227 • TPC21 Differential Phase vs Frequency 1 2 0 20 0 100 10 175°C LT1227 • TPC20 Output Impedance in Shutdown vs Frequency VS = ±15V AV = 1 RF = 1.5k 125°C 7 –8 20 25°C 9 6 LT1227 • TPC19 OUTPUT IMPEDANCE (kΩ) 10 –6 0 –55°C 11 –6 –10 3rd Order Intercept vs Frequency LT1227 • TPC24 Test Circuit for 3rd Order Intercept 45 –20 –40 3RD ORDER INTERCEPT (dBm) VS = ±15V VO = 2VP-P RL = 100Ω RF = 820Ω AV = 10dB –30 DISTORTION (dBc) SUPPLY CURRENT (mA) VS = ±15V RF = RG = 1k 8 OUTPUT STEP (V) Supply Current vs Supply Voltage 14 10 10 2ND 3RD –50 –60 VS = ±15V RL = 100Ω RF = 680Ω RG = 75Ω 40 + 50Ω LT1227 PO – 35 680Ω 30 75Ω 25 50Ω MEASURE INTERCEPT AT PO 20 1227 TC 15 –70 1 10 FREQUENCY (MHz) 100 LT1227 • TPC25 6 0 10 20 30 40 FREQUENCY (MHz) 50 60 LT1227 • TPC26 LT1227 W W SI PLIFIED SCHE ATIC 7 14k NULL 1 V+ NULL 5 CURRENT SOURCE BIAS 8 S/D +IN 3 2 –IN 6 VOUT 4 V– 1227 SS U W U UO APPLICATI S I FOR ATIO The LT1227 is a very fast current feedback amplifier. Because it is a current feedback amplifier, the bandwidth is maintained over a wide range of voltage gains. The amplifier is designed to drive low impedance loads such as cables with excellent linearity at high frequencies. Feedback Resistor Selection The small-signal bandwidth of the LT1227 is set by the external feedback resistors and the internal junction capacitors. As a result, the bandwidth is a function of the supply voltage, the value of the feedback resistor, the closed-loop gain and load resistor. The characteristic curves of Bandwidth vs Supply Voltage show the effect of a heavy load (100Ω) and a light load (1k). 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. At a gain of two, on ±15V supplies with a 1k feedback resistor, the bandwidth into a light load is over 140MHz, but into a heavy load the bandwidth reduces to 120MHz. The loading has this effect because there is a mild resonance in the output stage that enhances the bandwidth at light loads but has its Q reduced by the heavy load. This enhancement is only useful at low gain settlings; at a gain of ten it does not boost the bandwidth. At unity gain, the enhancement is so effective the value of the feedback resistor has very little effect. At very high closed-loop gains, the bandwidth is limited by the gain bandwidth product of about 1GHz. The curves show that the bandwidth at a closed-loop gain of 100 is 12MHz, only one tenth what it is at a gain of two. 7 LT1227 U W U UO APPLICATI S I FOR ATIO 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 5.0µA per volt of supply mismatch, though typically the change is less than 0.5µA per volt. Small-Signal Rise Time, AV = +2 Slew Rate VOUT RF = 1k, RG= 1k, RL = 100Ω AI01 Capacitance on the Inverting Input 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. Capacitive Loads The LT1227 can drive capacitive loads directly when the proper value of feedback resistor is used. The graph of Maximum Capacitive Load vs Feedback Resistor should be used to select the appropriate value. The value shown is for 5dB peaking when driving a 1k load at a gain of 2. This is a worst case condition, the amplifier is more stable at higher gains and driving heavier loads. Alternatively, a small resistor (10Ω to 20Ω) can be put in series with the output to isolate the capacitive load from the amplifier output. This has the advantage that the amplifier bandwidth is only reduced when the capacitive load is present and the disadvantage that the gain is a function of the load resistance. The slew rate of a current feedback amplifier is not independent of the amplifier gain configuration the way slew rate is in a traditional op amp. This is because both the input stage and the output stage have slew rate limitations. In the inverting mode, and for higher gains in the noninverting mode, the signal amplitude between the input pins is small and the overall slew rate is that of the output stage. For gains less than ten in the noninverting mode, the overall slew rate is limited by the input stage. The input stage slew rate of the LT1227 is approximately 125V/µs and is set by internal currents and capacitances. The output slew rate is set by the value of the feedback resistors and the internal capacitances. At a gain of ten with a 1k feedback resistor and ±15V supplies, the output slew rate is typically 1100V/µs. Larger feedback resistors will reduce the slew rate as will lower supply voltages, similar to the way the bandwidth is reduced. The graph of Maximum Undistorted Output vs Frequency relates the slew rate limitations to sinusoidal inputs for various gain configurations. Large-Signal Transient Response, AV = +10 VOUT Power Supplies The LT1227 will operate from single or split supplies from ±2V (4V total) to ±15V (30V total). It is not necessary to use equal value split supplies, however the offset voltage 8 RF = 910Ω, RG= 100Ω, RL = 400Ω AI02 LT1227 U W U UO APPLICATI S I FOR ATIO Shutdown Large-Signal Transient Response, AV = +2 VOUT RF = 1k, RG= 1k, RL = 400Ω AI03 Large-Signal Transient Response, AV = –2 The LT1227 has a high impedance, low supply current mode which is controlled by pin 8. In the shutdown mode, the output looks like a 12pF capacitor and the supply current drops to approximately the pin 8 current. The shutdown pin is referenced to the positive supply through an internal pullup circuit (see the simplified schematic). Pulling a current of greater than 50µA from pin 8 will put the device into the shutdown mode. An easy way to force shutdown is to ground pin 8, using open drain (collector) logic. 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 an internal JFET limits the pin 8 current to about 100µA. When pin 8 is open, the LT1227 operates normally. Differential Input Signal Swing VOUT AI04 RF = 1k, RG= 510Ω, RL = 400Ω AI04 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 maximum allowable input voltage. To allow for some margin, it is recommended that the input signal be less than ±5V when the device is shutdown. Offset Adjust Settling Time The characteristic curves show that the LT1227 amplifier settles to within 10mV of final value in 40ns to 55ns for any output step up to 10V. The curve of settling to 1mV of final value shows that there is a slower thermal contribution up to 20µs. The thermal settling component comes from the output and the input stage. The output contributes just under 1mV per volt of output change and the input contributes 300µV per volt of input change. Fortunately the input thermal tends to cancel the output thermal. For this reason the noninverting gain of two configuration settles faster than the inverting gain of one. Pins 1 and 5 are provided for offset nulling. A small current to V + or ground will compensate for DC offsets in the device. The pins are referenced to the positive supply (see the simplified schematic) and should be left open if unused. The offset adjust pins act primarily on the inverting input bias current. A 10k pot connected to pins 1 and 5 with the wiper connected to V + will null out the bias current, but will not affect the offset voltage much. Since the output offset is VO ≅ AV • VOS + (IIN –) • RF at higher gains (AV > 5), the VOS term will dominate. To null out the VOS term, use a 10k pot between pins 1 and 5 with a 150k resistor from the wiper to ground for 15V split supplies, 47k for 5V split supplies. 9 LT1227 UO TYPICAL APPLICATI S MUX Amplifier MUX Amplifier The shutdown function can be effectively used to construct a MUX amplifier. A two-channel version is shown, but more inputs could be added with suitable logic. By configuring each amplifier as a unity-gain follower, there is no loading by the feedback network when the amplifier is off. The open drains of the 74C906 buffers are used to interface the 5V logic to the shutdown pin. Feedthrough from the unselected input to the output is –70dB at 10MHz. The differential voltage between MUX inputs VIN1 and VIN2 appears across the inputs of the shutdown device, this voltage should be less than ±5V to avoid turning on the clamp diodes discussed previously. If the inputs are sinusoidal having a zero DC level, this implies that the amplitude of each input should be less than 5VP-P. The output impedance of the off amplifier remains high until the output level exceeds approximately 6VP-P at 10MHz, this sets the maximum usable output level. Switching time between inputs is about 4µs without an external pullup. Adding a 10k pullup resistor from each shutdown pin to V + will reduce the switching time to 2µs but will increase the positive supply current in shutdown by 1.5mA. 15V + VIN1 LT1227 S/D VOUT – –15V 1.5k VOUT =1 VIN 5V 74C906 15V + VIN2 LT1227 S/D – –15V 1.5k 5V 5V INPUT SELECT 74HC04 74C906 1227 TA04 MUX Output MUX Input Crosstalk vs Frequency –40 INPUT CROSSTALK (dB) –50 VOUT INPUT SELECT –60 –70 –80 –90 VIN1 = 1VP-P, VIN2 = 0V TA03 1 10 FREQUENCY (MHz) 100 LT1227 TA05 10 LT1227 UO TYPICAL APPLICATI S Single Supply AC-Coupled Amplifier Inverting Single Supply AC-Coupled Amplifier Noninverting 5V 5V 4.7µF + + 4.7µF AV = 10k 22µF 10k BW = 14Hz to 60MHz + VIN 510Ω ≈ 10 RS + 51Ω + VOUT LT1227 10k + + 2.2µF – – 220µF VOUT LT1227 10k 220µF + + RS 510Ω 51Ω VIN AV = 11 BW = 14Hz to 60MHz 510Ω 51Ω 1227 TA09 1227 TA08 Buffer with DC Nulling Loop V+ 3.58MHz Oscillator 15V 180Ω 1N4148 100k 180Ω 10k 10k 2N3904 0.1µF 100pF 75pF 3 VIN 3.579545MHz 68pF 150k 5 + 2 1k 1 6 LT1227 10k VOUT – 15V 1.5k – 51Ω 100k VOUT LT1227 0.01µF + + –15V 1227 TA10 100k LT1097 – 0.01µF CMOS Logic to Shutdown Interface 1227 TA07 15V 3 7 + 2 Optional Offset Nulling circuit 6 LT1227 8 – RNULL V+ 4 5V –15V 3 10k 10k 7 + 2N3904 1 LT1227 2 1227 TA11 5 – 4 6 RNULL = 47k FOR VS = ±5V RNULL = 150k FOR VS = ±15V 1227 TA12 V– 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 LT1227 U PACKAGE DESCRIPTIO J8 Package 8-Lead Ceramic DIP 0.200 (5.080) MAX 0.290 – 0.320 (7.366 – 8.128) 0.015 – 0.060 (0.381 – 1.524) 0.008 – 0.018 (0.203 – 0.457) 0.405 (10.287) MAX 0.005 (0.127) MIN 8 6 7 5 0.025 (0.635) RAD TYP 0.220 – 0.310 (5.588 – 7.874) 0° – 15° 1 0.045 – 0.068 (1.143 – 1.727) 0.385 ± 0.025 (9.779 ± 0.635) 2 3 4 0.125 3.175 0.100 ± 0.010 MIN (2.540 ± 0.254) 0.014 – 0.026 (0.360 – 0.660) CORNER LEADS OPTION (4 PLCS) NOTE: LEAD DIMENSIONS APPLY TO SOLDER DIP OR TIN PLATE LEADS. 0.023 – 0.045 (0.584 – 1.143) HALF LEAD OPTION J8 0293 0.045 – 0.068 (1.143 – 1.727) FULL LEAD OPTION N8 Package 8-Lead Plastic DIP 0.300 – 0.320 (7.620 – 8.128) 0.009 – 0.015 (0.229 – 0.381) ( +0.025 0.325 –0.015 +0.635 8.255 –0.381 ) 0.130 ± 0.005 (3.302 ± 0.127) 0.045 – 0.065 (1.143 – 1.651) 0.400 (10.160) MAX 8 7 6 0.065 (1.651) TYP 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 0.018 ± 0.003 (0.457 ± 0.076) N8 0392 0.053 – 0.069 (1.346 – 1.752) 0°– 8° TYP 0.016 – 0.050 0.406 – 1.270 7 6 5 0.004 – 0.010 (0.101 – 0.254) 0.150 – 0.157* (3.810 – 3.988) 0.228 – 0.244 (5.791 – 6.197) 0.014 – 0.019 (0.355 – 0.483) *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006 INCH (0.15mm). 12 0.189 – 0.197* (4.801 – 5.004) 8 0.010 – 0.020 × 45° (0.254 – 0.508) 4 3 S8 Package 8-Lead Plastic SOIC 0.008 – 0.010 (0.203 – 0.254) 5 Linear Technology Corporation 0.050 (1.270) BSC 1 2 3 4 SO8 0294 LT/GP 0394 5K REV A 1630 McCarthy Blvd., Milpitas, CA 95035-7487 (408) 432-1900 ● FAX: (408) 434-0507 ● TELEX: 499-3977 LINEAR TECHNOLOGY CORPORATION 1994