Complementary current reusing preamp for operational amplifier

Patent metadata

Field	Value
Publication number	US-10305502-B2
Application number	US-201816027669-A
Country	US
Kind code	B2
Filing date	Jul 5, 2018
Priority date	Jun 19, 2014
Publication date	May 28, 2019
Grant date	May 28, 2019

Abstract

An apparatus includes a preamplifier stage to receive a power supply voltage and generate an output based upon an input. In particular, the preamplifier stage includes a biasing device coupled between the output and a ground node to bias a DC voltage level of the output independently of the power supply voltage. The preamplifier stage also includes a complementary circuit to receive the input and generate the output. The complementary circuit reuses a current through the preamplifier stage to provide an increased transconductance of the preamplifier stage for a given current level.

First claim

What is claimed is:

1. An apparatus comprising:
a preamplifier stage including:
an output;
a current source;
a PMOS differential pair coupled to a power supply side of the preamplifier stage, sources of the PMOS differential pair being coupled to the current source;
an NMOS differential pair coupled to a ground side of the preamplifier stage, drains of the NMOS differential pair being coupled to respective drains of the PMOS differential pair at the output;
a diode-connected device coupled to the output and ground; and
a cross-coupled circuit coupled to the diode-connected device to adjust a gain of the preamplifier stage;
wherein in the gain of the preamplifier is given by a ratio of a transconductance of the PMOS differential pair and the NMOS differential pair to a transconductance of the diode-connected device divided by N−1 where N is a ratio of size of the diode-connected device to the cross-coupled circuit.

2. The apparatus of claim 1 wherein the preamplifier stage further comprises one or more short-channel devices to regulate the current through the preamplifier stage.

3. The apparatus of claim 2 wherein the preamplifier stage further comprises a resistive feedback circuit coupled to the diode-connected device to adjust a gain of the preamplifier stage.

4. The apparatus of claim 1 further comprising a feedback loop coupled to the preamplifier stage, the feedback loop to:
sense a DC voltage level of the output;
if the DC voltage level is above a predetermined threshold, reduce an amount of current injected to the preamplifier stage; and
if the DC voltage level is below a predetermined threshold, increase an amount of current injected into the preamplifier stage;
wherein the reduction in current injected results in a decrease of the DC voltage level of the output and the increase in current injected results in an increase of the DC voltage level.

5. The apparatus of claim 4 wherein the feedback loop controls a gate voltage of a short-channel device to vary the amount of current injected into the preamplifier stage.

6. The apparatus of claim 4 wherein the DC voltage level maintained by the feedback loop is substantially constant in varying thermal conditions.

Assignees

• Texas Instruments Inc

Inventors

• Hsieh Tien-Ling

Classifications

• H03G1/0029

  using field-effect transistors [FET] · CPC title

• H03F2203/45116

  Feedback coupled to the input of the differential amplifier · CPC title

• H03F1/42 Primary

  Modifications of amplifiers to extend the bandwidth · CPC title

• H03F2203/45112

  the biasing of the differential amplifier being controlled from the input or the output signal · CPC title

• H03F2200/36

  the amplifier comprising means for increasing the bandwidth · CPC title