Datasheet LT1251, LT1256 (Analog Devices)
| Fabricante | Analog Devices |
| Descripción | 40MHz Video Fader and DC Gain Controlled Amplifier |
| Páginas / Página | 24 / 1 — FEATURES. DESCRIPTION. Accurate Linear Gain Control:. 1% Typ,. 3% Max. … |
| Formato / tamaño de archivo | PDF / 396 Kb |
| Idioma del documento | Inglés |
FEATURES. DESCRIPTION. Accurate Linear Gain Control:. 1% Typ,. 3% Max. Constant Gain with Temperature. APPLICATIONS
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LT1251/LT1256 40MHz Video Fader and DC Gain Controlled Amplifier
U FEATURES DESCRIPTION
■
Accurate Linear Gain Control:
±
1% Typ,
±
3% Max
The LT®1251/LT1256 are 2-input, 1-output, 40MHz cur- ■
Constant Gain with Temperature
rent feedback amplifiers with a linear control circuit that ■ Wide Bandwidth: 40MHz sets the amount each input contributes to the output. ■ High Slew Rate: 300V/µs These parts make excellent electronically controlled vari- ■ Fast Control Path: 10MHz able gain amplifiers, filters, mixers and faders. The only ■ Low Control Feedthrough: 2.5mV external components required are the power supply by- ■ High Output Current: 40mA pass capacitors and the feedback resistors. Both parts ■ Low Output Noise operate on supplies from ±2.5V (or single 5V) to ±15V 45nV/√Hz at AV = 1 (or single 30V). 270nV/√Hz at AV = 100 Absolute gain accuracy is trimmed at wafer sort to mini- ■ Low Distortion: 0.01% mize part-to-part variations. The circuit is completely ■ Wide Supply Range: ±2.5V to ±15V temperature compensated. ■ Low Supply Current: 13mA ■ Low Differential Gain and Phase: 0.02%, 0.02° The LT1251 includes circuitry that eliminates the need for
U
accurate control signals around zero and full scale. For
APPLICATIONS
control signals of less than 2% or greater than 98%, the LT1251 sets one input completely off and the other ■ Composite Video Gain Control completely on. This is ideal for fader applications because ■ RGB, YUV Video Gain Control it eliminates off-channel feedthrough due to offset or gain ■ Video Faders, Keyers errors in the control signals. ■ Gamma Correction Amplifiers ■ Audio Gain Control, Faders The LT1256 does not have this on/off feature and operates ■ Multipliers, Modulators linearly over the complete control range. The LT1256 is ■ Electronically Tunable Filters recommended for applications requiring more than 20dB of linear control range. , LTC and LT are registered trademarks of Linear Technology Corporation.
U TYPICAL APPLICATION LT1256 Two-Input Video Fader Gain Accuracy vs Control Voltage
5 V 4 S = ±5V 1 LT1251/LT1256 14 VFS = 2.5V IN1 + + IN2 3 1 2 2 – – 13 2 CONTROL 0V TO 2.5V 3 12 2.5VDC 1 + + CONTROL C I I INPUT C FS FS 0 4 – – 11 I I FS C RF2 RF1 –1 1.5k 1.5k 5 5k 5k 10 GAIN ACCURACY (%) –2 6 9 –3 NULL V+ VC –4 GAIN ACCURACY (%) = A 100 ( ) VMEAS – ( 2.5 ) 7 8 V– –5 0 0.5 1.0 1.5 2.0 2.5 VOUT 1251/56 TA01 CONTROL VOLTAGE (V) 1251/56 TA02 1
U FEATURES DESCRIPTION
■
Accurate Linear Gain Control:
±
1% Typ,
±
3% Max
The LT®1251/LT1256 are 2-input, 1-output, 40MHz cur- ■
Constant Gain with Temperature
rent feedback amplifiers with a linear control circuit that ■ Wide Bandwidth: 40MHz sets the amount each input contributes to the output. ■ High Slew Rate: 300V/µs These parts make excellent electronically controlled vari- ■ Fast Control Path: 10MHz able gain amplifiers, filters, mixers and faders. The only ■ Low Control Feedthrough: 2.5mV external components required are the power supply by- ■ High Output Current: 40mA pass capacitors and the feedback resistors. Both parts ■ Low Output Noise operate on supplies from ±2.5V (or single 5V) to ±15V 45nV/√Hz at AV = 1 (or single 30V). 270nV/√Hz at AV = 100 Absolute gain accuracy is trimmed at wafer sort to mini- ■ Low Distortion: 0.01% mize part-to-part variations. The circuit is completely ■ Wide Supply Range: ±2.5V to ±15V temperature compensated. ■ Low Supply Current: 13mA ■ Low Differential Gain and Phase: 0.02%, 0.02° The LT1251 includes circuitry that eliminates the need for
U
accurate control signals around zero and full scale. For
APPLICATIONS
control signals of less than 2% or greater than 98%, the LT1251 sets one input completely off and the other ■ Composite Video Gain Control completely on. This is ideal for fader applications because ■ RGB, YUV Video Gain Control it eliminates off-channel feedthrough due to offset or gain ■ Video Faders, Keyers errors in the control signals. ■ Gamma Correction Amplifiers ■ Audio Gain Control, Faders The LT1256 does not have this on/off feature and operates ■ Multipliers, Modulators linearly over the complete control range. The LT1256 is ■ Electronically Tunable Filters recommended for applications requiring more than 20dB of linear control range. , LTC and LT are registered trademarks of Linear Technology Corporation.
U TYPICAL APPLICATION LT1256 Two-Input Video Fader Gain Accuracy vs Control Voltage
5 V 4 S = ±5V 1 LT1251/LT1256 14 VFS = 2.5V IN1 + + IN2 3 1 2 2 – – 13 2 CONTROL 0V TO 2.5V 3 12 2.5VDC 1 + + CONTROL C I I INPUT C FS FS 0 4 – – 11 I I FS C RF2 RF1 –1 1.5k 1.5k 5 5k 5k 10 GAIN ACCURACY (%) –2 6 9 –3 NULL V+ VC –4 GAIN ACCURACY (%) = A 100 ( ) VMEAS – ( 2.5 ) 7 8 V– –5 0 0.5 1.0 1.5 2.0 2.5 VOUT 1251/56 TA01 CONTROL VOLTAGE (V) 1251/56 TA02 1