US 5,345,123 A · Attenuator circuit operating with single point control

Abstract

An attenuator circuit uses single point control to adjust the attenuation levels between first and second nodes. The attenuator is set-up as a .pi.-network with a pass transistor and first and second shunt transistors. Capacitors are coupled in the drain and source conduction paths of the first and second shunt transistors for DC isolation to float the shunt transistors. A control voltage applied at the drain of the pass transistor and the gates of the first and second shunt transistors controls the attenuation level. A parallel resistor and capacitor combination at the drain of the first shunt transistor provides tuning to match the input impedance of the attenuator to the sourcing circuit.

Claims20

Dependent claims

An attenuator circuit, comprising:

a first transistor having a gate, a drain and a source, said drain receiving an input signal, said gate being coupled to a power supply conductor;
a second transistor having a gate, a drain and a source, said gate receiving a control voltage, said drain receiving a reference voltage;
first means coupled between said drain of said first transistor and said drain of said second transistor for providing DC isolation;
second means coupled between said source of said second transistor and said power supply conductor for providing DC isolation;
a third transistor having a gate, a drain and a source, said gate receiving said control voltage, said drain receiving said reference voltage;
third means coupled between said source of said first transistor and said drain of said third transistor for providing DC isolation;
and
fourth means coupled between said source of said third transistor and said power supply conductor for providing DC isolation.

5 more elements

Dependencies are inferred from the claim text.

Attenuator circuit operating with single point control

Life of this patent

Attenuator circuit operating with single point control

Life of this patent

Abstract

Claims20