VCA821

The VCA821 from Texas Instruments is a DC-coupled, wideband, linear in dB, continuously variable, voltage-controlled gain amplifier. It provides differential input to single-ended conversion with a high-impedance gain control input. The gain can be varied down 40 dB from the nominal maximum gain, which is set externally by gain and feedback resistors. The maximum gain is intended to be set between 6 dB and 32 dB.

Key electrical characteristics include a 710 MHz small-signal bandwidth at a gain of +2 V/V, and a 320 MHz bandwidth at a gain of +10 V/V. It features a 0.1-dB gain flatness to 135 MHz and a high slew rate of 2500 V/µs. The device operates from ±5-V supplies and offers a gain adjust range greater than 40 dB. High gain accuracy is achieved, with 20 dB typically within ±0.3 dB.

The VCA821's internal architecture integrates input buffers and an output current feedback amplifier with a multiplier core, eliminating the need for external buffering. It provides a high output current of ±90 mA. The gain control voltage adjusts the gain linearly in dB as it varies from 0V to +2 V. For example, at a maximum gain of 20 dB, the VCA821 provides 20 dB at V G = +2 V, down to less than -20 dB at V G = 0 V.

Available in SOIC (D) and VSSOP (DGS) packages, the VCA821 is suitable for surface mount applications. Its operating temperature range is -40°C to 85°C.