How to find the right Variable Gain Amplifiers AI guide
Written by an AI model from its trained knowledge.
What the AI looks for in Variable Gain Amplifiers
- Gain range and control law
- Check the total gain range in dB. Check whether control is linear-in-dB, which is preferred for AGC loops, or linear-in-voltage. Linear-in-dB control keeps AGC loop dynamics constant across the range.
- Analog vs digital control
- Analog voltage control suits continuous AGC. Digital or programmable-gain parts suit stepped, repeatable gain under MCU control. The control interface determines how the part fits your system.
- Bandwidth at all gains
- Verify bandwidth across the full gain range, not just at minimum gain. Some VGAs lose bandwidth at high gain.
- Noise figure and distortion
- Check noise at maximum gain, where sensitivity matters, and distortion at minimum gain, where signals are large. These figures determine usable dynamic range in receivers, ultrasound and audio.
- Domain
- Audio uses dedicated audio VCAs. RF and IF, ultrasound and instrumentation use wideband VGAs. Parts are optimized for very different frequency ranges and distortion profiles.
Brands that matter
- Analog Devices: Has a wide range of VGAs including the AD603/AD8338 families for RF, ultrasound and AGC.
- Texas Instruments: Makes VCA-series wideband VGAs and programmable-gain amplifiers.
- THAT Corporation: Specializes in professional audio VCAs.
- Qorvo: Makes RF digital step attenuators and gain blocks for RF chains.
What to avoid
- Using a digital potentiometer as a VGA in wideband or low-distortion paths.
- Choosing a wideband RF VGA for audio, or an audio VCA for RF.
- Ignoring the settling time of the gain control when switching gain rapidly.
Questions
Is a PGA the same as a VGA?
A PGA (programmable-gain amplifier) is a VGA with discrete, digitally selected gain steps. A classic VGA varies gain continuously with an analog control voltage.