US 4,607,232 A · Low voltage amplifier circuit

Abstract

An electronic circuit is provided comprising: a pair of transistors having collector electrodes connected together at an output terminal and emitter electrodes coupled to opposite potentials of a voltage supply; a current source; and, means, responsive to a current produced by the current source, for establishing bias currents to base electrodes of the pair of transistors in accordance with an input signal, such bias currents being dependent on the current produced by the current source and being substantially independent of, over a nominal operating supply voltage range of the circuit, of variations in the voltage supply. With such arrangement, since the bias current to the transistors are provided from a current source, the bias currents are independent of the voltage supply and the circuit may operate with less than a one volt voltage supply. In accordance with a preferred embodiment of the invention, a resistor is coupled between the voltage supply and an emitter of one of the pair of transistors. With such arrangement current gain is provided. Further, the supply voltage may be as low as 2V.sub.CE(SAT) +IR where IR is the voltage drop across the resistor, typically 30 millivolts. Hence, the minimum supply voltage is still less than one volt.

Claims12

Dependent claims

An electrical circuit comprising:

(a) a pair of transistors having collector electrodes connected together at an output terminal and emitter electrodes coupled to a voltage supply;
(b) a current source;
and,
(c) means, responsive to current produced by the current source, for establishing bias currents to base electrodes of the pair of transistors in accordance with an input signal, such bias currents being dependent on the current produced by the current source and being substantially independent, over a nominal operating voltage range of the circuit, of variations in the voltage supply, said bias current establishing means comprising:
(i) a third transistor having an emitter electrode coupled to the emitter electrode of a first one of the pair of transistors and a collector electrode coupled to the base electrode of a second one of the pair of transistors;
and
(ii) means, comprising a current mirror, for dividing current produced by the current source between the base electrode of the third transistor and the base electrode of the first one of the pair of transistors selectively in accordance with the input signal.

4 more elements

Dependencies are inferred from the claim text.

Low voltage amplifier circuit

Life of this patent

Low voltage amplifier circuit

Life of this patent

Abstract

Claims12