Self biasing differential amplifier
OwnerTed R. Trillinginventor
Life of this patent
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Abstract
A self biasing low input impedance differential amplifier for current mode applications requiring wide bandwidth with response down to DC. A shunt-shunt differential mode feedback system in combination with a series-shunt common mode feedback system is connected between an input amplifier stage and an output amplifier stage. An additional shunt-series common mode feedback signal is applied to the input stage to short out the common mode component of the amplifier input signal and minimize input signal drift. High open loop gain in the differential feedback loop provides low impedance amplifier inputs.
Claims11
A differential amplifier system comprising, in combination:
- input amplifier means adapted to receive an input signal having common mode and differential mode components and connected to receive a first common mode feedback signal and differential mode feedback signal, and for producing a first output signal;
- output amplifier means connected to receive said first output signal for producing a second output signal to a load, a third output signal to a first active feedback means, and a fourth output signal to a second active feedback means, said second output signal being an amplified replica of said first output signal, said third and fourth output signals being the differential and common mode components, respectively, of said second output signal;
- first active feedback means connected to receive said third output signal and a second common mode feedback signal for providing the differential mode feedback signal to said input amplifier means for controlling the impedance thereof;
- second active feedback means including a transistor having a base connected to receive said fourth output signal and a collector for providing said first common mode feedback signal to said input amplifier means for controlling the impedance thereof;
- and
- third active feedback means connected to receive said first common mode feedback signal and a reference voltage level for providing said second common mode feedback signal to said first feedback means;
- whereby the common mode component of said input signal is canceled and the input signal is self-biased to a predetermined voltage level.
A differential amplifier system comprising in combination:
- input amplifier means adapted to receive an input signal having common mode and differential mode components and connected to receive a first common mode feedback signal, for producing a first output signal;
- output amplifier means connected to receive the first output signal, for supplying a second output signal, which is an amplified replica of the first output signal, to a load, and third and fourth signals which are the differential mode and common mode components, respectively, of the second output signal;
- first active feedback means connected to receive the third and fourth output signals for providing common mode and differential mode feedback signals to the input of said input amplifier means for controlling the impedance thereof;
- and
- second active feedback means connected to receive the first common mode feedback signal and a reference voltage level for providing a second common mode feedback signal to said first active feedback means;
- whereby the common mode component of said input signal is cancelled and the input signal is self-biased to a predetermined voltage level.
Dependencies are inferred from the claim text.