US 6,570,448 B1 · System and method for a startup circuit for a differential CMOS amplifier

Abstract

A system is provided for correcting start-up deficiencies in an amplifier. The system includes a comparing device configured to (i) receive a second circuit node voltage and a reference voltage as inputs, (ii) compare the received second circuit node voltage and the reference voltage, and (iii) produce a compensating voltage signal based upon the comparison. Next, an active device has a control terminal connected to an output port of the comparing device and is configured to receive the compensating voltage signal. The active device also includes an output terminal connected to the control terminal of the second active device, and a common terminal connected to a first circuit node. Another active device has a control terminal connected to the output port of the comparing device and is configured to receive the compensating voltage signal. The other active device also has an output terminal connected to the control terminal of the first active device, and a common terminal connected to the first circuit node.

Claims17

Dependent claims

A method for correcting start-up deficiencies in an amplifier using a startup mechanism, the amplifier including (i) first and second transistors having sources thereof connected to a first circuit node, and drains thereof respectively forming first and second amplifier output ports and (ii) third and fourth transistors having gates thereof respectively forming first and second amplifier input ports, drains thereof being respectively connected, at least indirectly, to the gates of the first and second transistors, and sources thereof being connected together and forming a second circuit node, a second circuit node voltage being representative of a voltage level of the second circuit node;

the startup mechanism including:
a comparator having inverting and non-inverting input ports and an output port;
and
fifth and sixth transistors having (i) gates connected to the comparator output port, (ii) drains respectively connected to the gates of the first and second transistors, and (iii) sources connected to the first circuit node;
the method comprising:
comparing the second circuit node voltage to a reference voltage;
producing a compensating voltage based upon the comparison;
and
adjusting a voltage of the first and second amplifier output ports in accordance with the compensating voltage.

6 more elements

A startup circuit for an amplifier, the amplifier including first and second active devices having common terminals connected to a first circuit node and output terminals respectively forming first and second amplifier output ports;

and
third and fourth active devices having control terminals thereof respectively forming first and second amplifier input ports, output terminals thereof being respectively connected, at least indirectly, to the control terminals of the first and second active devices, and common terminals thereof being connected together and forming a second circuit node, a second circuit node voltage being representative of a voltage level of the second circuit node;
the startup circuit comprising:
a comparing device configured to (i) receive the second circuit node voltage and a reference voltage as inputs, (ii) compare the received second circuit node voltage and the reference voltage, and (iii) produce a compensating voltage signal based upon the comparison;
a fifth active device having (i) a control terminal connected to an output port of the comparing device and being configured to receive the compensating voltage signal, (ii) an output terminal connected to the control terminal of the second active device, and (iii) a common terminal connected to the first circuit node;
and
a sixth active device having (i) a control terminal connected to the output port of the comparing device and being configured to receive the compensating voltage signal, (ii) an output terminal connected to the control terminal of the first active device, and (iii) a common terminal connected to the first circuit node.

4 more elements

A programmable gain amplifier (PGA) comprising:

first and second active devices having control terminals, common terminals, and output terminals, the common terminals being connected to a first circuit node and the output terminals respectively forming first and second PGA output ports;
third and fourth active devices having control terminals thereof respectively forming first and second PGA input ports, output terminals thereof being respectively connected, at least indirectly, to the control terminals of the first and second active devices, and common terminals thereof being connected together and forming a second circuit node, a second circuit node voltage being representative of a voltage level of the second circuit node;
a comparing device configured to (i) receive the second circuit node voltage and a reference voltage as inputs, (ii) compare the received second circuit node voltage and the reference voltage, and (iii) produce a compensating voltage signal based upon the comparison;
a fifth active device having (i) a control terminal connected to an output port of the comparing device and being configured to receive the compensating voltage signal, (ii) an output terminal connected to the control terminal of the second active device, and (iii) a common terminal connected to the first circuit node;
and
a sixth active device having (i) a control terminal connected to the output port of the comparing device and being configured to receive the compensating voltage signal, (ii) an output terminal connected to the control terminal of the first active device, and (iii) a common terminal connected to the first circuit node.

3 more elements

Dependencies are inferred from the claim text.

System and method for a startup circuit for a differential CMOS amplifier

Life of this patent

System and method for a startup circuit for a differential CMOS amplifier

Life of this patent

Abstract

Claims17