Complementary current reusing preamp for operational amplifier
First Claim
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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.
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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.
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6 Claims
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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.- View Dependent Claims (2, 3, 4, 5, 6)
Specification