A Buffer Amplifier provides isolation (S12) as well as gain between two circuit elements. Most commonly the buffered element is an oscillator, and the purpose of the buffer amplifier is to ensure poor impedance match at a mixer port does not "pull" or alter the output frequency of the oscillator. In some cases, the buffer is also used to provide a constant drive level to the following component.
Buffer amplifiers need to have good impedance matches, so as not to load the components they are buffering. Since isolation is an important characteristic of a buffer amplifier, shunt feedback is usually avoided as a matching approach - the feedback element would provide an alternate path for the input signal and decrease the isolation of the amplifier.
The term "Buffer Amplifier" is also commonly used loosely to refer to any gain stage amplifier.
Agilent Technologies Products for Buffer Amplifier Applications
- Discrete Devices:
- Bipolar Transistors as Buffer Amplifiers
- GaAs FETs as Buffer Amplifiers
- Integrated Circuits:
- ICs for RF/uW Buffers
- Isolation comparison - RF/uW ICs
- ICs for millimeter wave Receivers, Direct Tansmitters, or Upconverting Transmitters
- Isolation comparison - mmw ICs