Texas Instruments VCA821IDGST

Overview

VCA821IDGST from Texas Instruments is a DC-coupled, ultra-wideband voltage-controlled amplifier (VGA) with linear-in-dB gain control, 710-MHz small-signal bandwidth at G = +2 V/V, >40-dB gain adjust range, and ±90 mA output current. It serves as a core signal conditioning element in AGC receivers and differential line receivers requiring precise amplitude scaling across RF and video frequencies.

For engineers reviewing the VCA821IDGST datasheet, VCA821IDGST pinout, VCA821IDGST application, or VCA821IDGST equivalent, key selection criteria include gain linearity (±0.3 dB over 1–2 V control range), 0.1-dB flatness to 135 MHz, slew rate of 2500 V/μs, and compatibility with ±5-V supplies and 10-pin VSSOP packaging.

Technical Context

The VCA821IDGST integrates two input buffers and a current-feedback output stage with an internal multiplier core, enabling full VGA functionality without external buffering. Its gain is set externally via RG and RF resistors, with nominal maximum gain configurable between 6 dB and 32 dB.

Gain control is linear-in-dB: at AVMAX = 20 dB, VG = +2 V yields +20 dB gain, while VG = 0 V yields < –20 dB. The device maintains high accuracy (±0.4 dB absolute gain error at +25°C) and supports differential input-to-single-ended output conversion with 6.0 nV/√Hz input voltage noise.

Key Specifications

Pinout & Package

The VCA821IDGST is housed in a 10-pin VSSOP package (3.00 mm × 3.00 mm), optimized for high-density PCB layouts and thermal performance (θJA = 173.1 °C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with VCA822IDR and VCA824IDGTR, the VCA821IDGST delivers the highest large-signal bandwidth and slew rate in the family, making it optimal for demanding RF, video, and pulse applications where transient fidelity and wideband flatness are critical.

Availability

VCA821IDGST is available at Aetrix Electronics and suitable for AGC receivers with RSSI, differential line receivers, and pulse amplitude compensation systems requiring stable component supply, consistent gain linearity, and guaranteed VSSOP-10 packaging.

Supply support for VCA821IDGST 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 specializing in analog, embedded processing, and connectivity technologies with over 90 years of innovation in precision signal chain solutions.

The VCA821IDGST belongs to TI's high-speed variable gain amplifier product line, engineered for wideband RF, video, and test equipment applications demanding linear-in-dB control, DC coupling, and high output drive.

FAQ

What is the maximum recommended gain setting for the VCA821IDGST?

The VCA821IDGST is designed for nominal maximum gain (AVMAX) between 6 dB and 32 dB, set externally using RG and RF resistors. At AVMAX = 20 dB, gain accuracy is specified as ±0.4 dB at +25°C. Exceeding 32 dB may degrade linearity and bandwidth; the datasheet explicitly advises against settings beyond this range to maintain 0.1-dB flatness and thermal stability in the VCA821IDGST.

Does the VCA821IDGST support single-supply operation?

No, the VCA821IDGST requires dual ±5-V supplies (±3.5 V to ±6 V) for full specification compliance. Its input common-mode range spans –2.1 V to +1.6 V, and output swing is symmetric about ground. Attempting single-supply operation violates absolute maximum ratings and causes clipping, distortion, or latch-up. The VCA821IDGST is inherently a dual-supply device due to its fully differential input stage and current-feedback output architecture.

What is the gain control input impedance of the VCA821IDGST?

The VCA821IDGST gain control input (VG pin) has an impedance of 1.5 MΩ in parallel with 0.6 pF, as confirmed in Section 7.5 of the datasheet. This high impedance minimizes loading on control DACs or filter networks, enabling simple RC filtering without significant gain error. Input bias current is 10–16 μA, and average drift is ±12 nA/°C - values critical for maintaining gain accuracy across temperature in the VCA821IDGST.

Can the VCA821IDGST drive a 50-Ω load directly?

Yes, the VCA821IDGST can drive a 50-Ω load directly, delivering ±3.2 V output swing at –40°C to +85°C (per Section 7.5). Its ±90 mA output current capability exceeds the 60 mA required for ±3 V into 50 Ω. However, layout best practices - including short traces, local decoupling, and proper grounding - are essential to maintain 710-MHz bandwidth and prevent instability. Driving 50 Ω is fully supported in the VCA821IDGST datasheet specifications.

How does the VCA821IDGST achieve 0.1-dB gain flatness to 135 MHz?

The VCA821IDGST achieves 0.1-dB gain flatness to 135 MHz through its current-feedback amplifier topology combined with internal compensation optimized for wideband stability. Unlike voltage-feedback amplifiers, its gain-bandwidth product is less dependent on closed-loop gain, enabling consistent flatness across the 6–32 dB AVMAX range. This performance is verified under defined test conditions (G = 20 dB, VO = 200 mVPP) and is a guaranteed characteristic of the VCA821IDGST, not a typical-only value.