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Buffer Amplifier

Agilent Technologies products:

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.

Schematic symbol:

Key Specifications
Isolation (S12)
Range: 20 - 55 dB
Output Power (Pout, P1 dB)
Range: -10 to +17 dBm
(0.1 to 50 mW)
Gain (G, S21)
Range: 0 to 30 dB per stage
VSWR: 1.2:1 to 2:1 typ.
Return Loss: -10 to -20 typ.
magnitude: tenths of dBs to dBs
phase: tenths to 10s of degrees

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
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this page last updated: 1 October 1999