LT1251/LT1256 40MHz Video Fader and DC Gain Controlled Amplifier FEATURES DESCRIPTION n Accurate Linear Gain Control: 1% Typ, 3% Max The LT 1251/LT1256 are 2-input, 1-output, 40MHz cur- n Constant Gain with Temperature rent feedback amplifiers with a linear control circuit that n Wide Bandwidth: 40MHz sets the amount each input contributes to the output. n High Slew Rate: 300V/s These parts make excellent electronically controlled vari- n Fast Control Path: 10MHz able gain amplifiers, filters, mixers and faders. The only n Low Control Feedthrough: 2.5mV external components required are the power supply by- n High Output Current: 40mA pass capacitors and the feedback resistors. Both parts n Low Output Noise operate on supplies from 2.5V (or single 5V) to 15V 45nV/Hz at A = 1 (or single 30V). V 270nV/Hz at A = 100 V Absolute gain accuracy is trimmed at wafer sort to mini- n Low Distortion: 0.01% mize part-to-part variations. The circuit is completely n Wide Supply Range: 2.5V to 15V temperature compensated. n Low Supply Current: 13mA n The LT1251 includes circuitry that eliminates the need for Low Differential Gain and Phase: 0.02%, 0.02 accurate control signals around zero and full scale. For U control signals of less than 2% or greater than 98%, the APPLICATIONS LT1251 sets one input completely off and the other n Composite Video Gain Control completely on. This is ideal for fader applications because n RGB, YUV Video Gain Control it eliminates off-channel feedthrough due to offset or gain n Video Faders, Keyers errors in the control signals. n Gamma Correction Amplifiers n The LT1256 does not have this on/off feature and operates Audio Gain Control, Faders n linearly over the complete control range. The LT1256 is Multipliers, Modulators n recommended for applications requiring more than 20dB Electronically Tunable Filters of linear control range. , LTC and LT are registered trademarks of Linear Technology Corporation. TYPICAL APPLICATION LT1256 Two-Input Video Fader Gain Accuracy vs Control Voltage 5 V = 5V S 4 LT1251/LT1256 V = 2.5V 1 14 FS IN1 IN2 + 3 1 2 2 13 2 CONTROL 1 3 12 0V TO 2.5V 2.5VDC + CONTROL I INPUT I CFC FSS 0 4 11 I I FS R R C F2 F1 1 1.5k 1.5k 5k 5k 5 10 2 3 6 9 + NULL V V C 100 4 GAIN ACCURACY (%) = A VMEAS () () 2.5 7 8 V 5 0 0.5 1.5 2.0 2.5 1.0 V 1251/56 TA01 OUT CONTROL VOLTAGE (V) 1251/56 TA02 1 GAIN ACCURACY (%) + + U ULT1251/LT1256 ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION + Total Supply Voltage (V to V ) .............................. 36V TOP VIEW ORDER PART Input Current ...................................................... 15mA NUMBER IN2 IN1 1 14 + + 1 Input Voltage on Pins 3,4,5,10,11,12 ............... V to V 2 FB2 FB1 2 13 CONTROL Output Short-Circuit Duration (Note 1) ........ Continuous LT1251CN + V V 3 12 FS C CFS Specified Temperature Range (Note 2) ....... 0C to 70C LT1251CS I I 4 11 FS C LT1256CN Operating Temperature Range ............... 40C to 85C R R 5 10 FS C LT1256CS Storage Temperature Range ................. 65C to 150C + V NULL 6 9 Junction Temperature (Note 3)............................ 150C (Note 2) V V 7 8 OUT Lead Temperature (Soldering, 10 sec).................. 300C N PACKAGE S PACKAGE 14-LEAD PDIP 14-LEAD PLASTIC SO T = 150C, = 70C/ W (N) JMAX JA T = 150C, = 100C/ W (S) JMAX JA Consult factory for Industrial and Military grade parts. SIG AL A PLIFIER AC CHARACTERISTICS 0C T 70C, V = 5V, V = 1V , f = 1kHz, A = 1, R = R = 1.5k, V = 2.5V, I = I = NULL = Open, Pins 5,10 = GND, A S IN RMS VMAX F1 F2 FS C FS unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS 2%IN1 2% Input 1 Gain V (Pin 3) = 0.05V LT1251 l 0 0.1 % C LT1256 l 0.1 5.0 % 10%IN1 10% Input 1 Gain V (Pin 3) = 0.25V l713 % C 20%IN1 20% Input 1 Gain V (Pin 3) = 0.50V l 17 23 % C 30%IN1 30% Input 1 Gain V (Pin 3) = 0.75V l 27 33 % C 40%IN1 40% Input 1 Gain V (Pin 3) = 1.00V l 37 43 % C 50%IN1 50% Input 1 Gain V (Pin 3) = 1.25V l 47 53 % C 60%IN1 60% Input 1 Gain V (Pin 3) = 1.50V l 57 63 % C 70%IN1 70% Input 1 Gain V (Pin 3) = 1.75V l 67 73 % C 80%IN1 80% Input 1 Gain V (Pin 3) = 2.00V l 77 83 % C 90%IN1 90% Input 1 Gain V (Pin 3) = 2.25V l 87 93 % C 98%IN1 98% Input 1 Gain V (Pin 3) = 2.45V LT1251 l 99.9 100.0 % C LT1256 l 95.0 99.9 % 2%IN2 2% Input 2 Gain V (Pin 3) = 2.45V LT1251 l 0 0.1 % C LT1256 l 0.1 5.0 % 10%IN2 10% Input 2 Gain V (Pin 3) = 2.25V l713 % C 20%IN2 20% Input 2 Gain V (Pin 3) = 2.00V l 17 23 % C 30%IN2 30% Input 2 Gain V (Pin 3) = 1.75V l 27 33 % C 40%IN2 40% Input 2 Gain V (Pin 3) = 1.50V l 37 43 % C 50%IN2 50% Input 2 Gain V (Pin 3) = 1.25V l 47 53 % C 60%IN2 60% Input 2 Gain V (Pin 3) = 1.00V l 57 63 % C 70%IN2 70% Input 2 Gain V (Pin 3) = 0.75V l 67 73 % C 80%IN2 80% Input 2 Gain V (Pin 3) = 0.50V l 77 83 % C 90%IN2 90% Input 2 Gain V (Pin 3) = 0.25V l 87 93 % C 98%IN2 98% Input 2 Gain V (Pin 3) = 0.05V LT1251 l 99.9 100.0 % C LT1256 l 95.0 99.9 % Gain Drift with Temperature V (Pin 3) = 0.75V N Package 50 ppm/C C (Worst Case at 30% Gain) V (Pin 3) = 0.75V S Package 400 ppm/C C 2 W U + + U W U U WWW