Texas Instruments VCA820ID

Overview

VCA820ID from Texas Instruments is a wideband, linear-in-dB voltage-controlled variable gain amplifier (VGA) with differential input and single-ended output. It delivers 150-MHz small-signal bandwidth, 137-MHz large-signal (5-VPP) bandwidth at +20 dB maximum gain, and >40-dB gain adjust range controlled by a 0–2 V analog voltage. It operates from ±5-V supplies and is used in AGC receivers, pulse amplitude compensation, and differential line receivers requiring precise gain control.

For engineers reviewing the VCA820ID datasheet, VCA820ID pinout, VCA820ID application, or VCA820ID equivalent, key selection criteria include its 20 dB ±0.4 dB gain accuracy, 1700-V/μs slew rate, 28 MHz 0.1-dB gain flatness, high CMRR (65–80 dB), and dual-package availability (SOIC-14 and VSSOP-10) for layout flexibility in RF and video signal chains.

Technical Context

The VCA820ID integrates two input buffers, a current-feedback output amplifier, and a multiplier core to form a complete dc-coupled VGA without external buffering. Its gain is set externally via RG and RF resistors, with nominal maximum gain configurable between +2 V/V and +100 V/V (e.g., 20 dB with RG = 200 Ω, RF = 1 kΩ).

Gain control is linear-in-dB: a 0–2 V VG input yields a monotonic 40-dB range centered on AVMAX (e.g., –20 dB to +20 dB for AVMAX = 20 dB). The device maintains ±0.4 dB gain error over temperature (–40°C to +85°C) and supports high-output-current operation (±160 mA) into low-impedance loads.

Key Specifications

Pinout & Package

Available in SOIC-14 (8.65 mm × 3.91 mm) and VSSOP-10 (3.00 mm × 3.00 mm) packages. Pin functions are identical across both packages except for NC and supply pin duplication in SOIC.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar variable gain amplifier applications.

Compared with VCA820ID, VCA822IDR offers identical package and bandwidth but relaxed gain accuracy, while VCA821IDGKR trades DC coupling and pin count for higher bandwidth-making VCA820ID the optimal choice for precision, wideband, dc-coupled gain control in AGC and pulse systems.

Availability

VCA820ID is available at Aetrix Electronics and suitable for AGC receivers, differential line receivers, and pulse amplitude compensation systems requiring stable component supply, consistent gain accuracy, and dual-package flexibility for prototyping and production.

Supply support for VCA820ID includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor leader delivering analog and embedded processing solutions for industrial, automotive, and communications markets.

The VCA820ID belongs to TI's wideband variable gain amplifier product line, designed specifically for high-fidelity, dc-coupled signal conditioning in RF, video, and test equipment where linear-in-dB control and precision gain stability are critical.

FAQ

What is the maximum gain accuracy specification for the VCA820ID?

The VCA820ID guarantees ±0.4 dB absolute gain error at AVMAX = 20 dB and +25°C, with ±0.6 dB error maintained across the full operating temperature range (–40°C to +85°C). This tight tolerance enables reliable closed-loop AGC performance without per-unit calibration. The VCA820ID achieves this using matched internal multiplier elements and precision resistor ratio dependencies defined by external RG and RF.

Does the VCA820ID support dc-coupled operation?

Yes, the VCA820ID is explicitly designed as a dc-coupled variable gain amplifier. Its differential inputs accept common-mode voltages from –2.1 V to +1.6 V, and its output swings rail-to-rail within ±3.9 V (into 100 Ω) with ±5-V supplies. This enables direct interfacing with baseband sensors, laser diode drivers, and pulse generators without AC-coupling capacitors that degrade low-frequency response.

What are the recommended external resistors for configuring VCA820ID at 20 dB maximum gain?

For AVMAX = 20 dB (+10 V/V), TI specifies RG = 200 Ω and RF = 1 kΩ with RL = 100 Ω load. This ratio yields precise gain setting while maintaining stability and bandwidth. The VCA820ID datasheet confirms these values deliver 137-MHz large-signal bandwidth and ±0.4 dB gain accuracy. Resistor tolerances ≤1% are recommended to preserve gain linearity and temperature stability.

Can the VCA820ID drive a 50-Ω transmission line directly?

Yes, the VCA820ID delivers ±160 mA output current and supports ±3.7 V swing into 100 Ω, which scales to ~±2.6 V into 50 Ω. While not optimized for 50-Ω source termination, it can drive short 50-Ω lines directly in non-reflective configurations. For robust 50-Ω matching, use a series 25-Ω resistor at the output-verified in TI's application notes for VCA820ID-based RF driver designs.

How does the gain control voltage (VG) relate to actual gain in dB for the VCA820ID?

The VCA820ID implements linear-in-dB control: gain (dB) = 20 × log₁₀(AVMAX) – 10 × log₁₀(1 + e^((VG – VCTRL₀)/VSLOPE)), where VCTRL₀ = 0.85 V and VSLOPE = 90 mV. At VG = 0 V, gain is ~–24 dB relative to AVMAX; at VG = 2 V, gain equals AVMAX. This exponential transfer function ensures uniform dB-step resolution across the full 40-dB range, simplifying AGC loop design.