High Gain Adjust Range, Wideband, Voltage-Controlled Amplifier

The VCA810 is a DC-coupled, wideband, continuously variable, voltage-controlled gain Amplifier It provides a differential input to single-ended output conversion with a high-impedance gain control input used to vary the gain over a 40dB to +40dB range linear in dB/V. Operating from 5V supplies, the gain control voltage for the VCA810 will adjust the gain from 40dB at 0V input to +40dB at 2V input. Increasing the control voltage above ground will attenuate the signal path to > 80dB. Signal bandwidth and slew rate remain constant over the entire gain adjust range. This 40dB/V gain control is accurate within 1.5dB (0.9dB for High Grade), allowing the gain control voltage in an AGC application to be used as a Received Signal Strength Indicator (RSSI) with 1.5dB accuracy. Excellent common-mode rejection and common-mode input range at the two high-impedance inputs allow the VCA810 to provide a differential receiver operation with gain adjust. The output signal is referenced to ground. Zero differential input voltage gives a 0V output with a small DC offset error. Low input noise voltage ensures good output SNR at the highest gain settings. In applications where pulse edge information is critical, and the VCA810 is being used to equalize varying channel loss, minimal change in group delay over gain setting will retain excellent pulse edge information. An improved output stage provides adequate output current to drive the most demanding loads. While principally intended to drive Analog-to-digital converters (ADCs) or 2nd-stage Amplifiers the 60mA output current will easily drive doubly-terminated 50 lines or a passive post Filter stage over the 1.7V output voltage range. By Texas Instruments