Read-out amplifier for photovoltaic detector

Claim 2

A read-out amplifier for a photovoltaic detector comprising: first switching means coupling, in a low impedance state, a source of bias potential to an output terminal of the photovoltaic detector; integrator means having an input coupled to the detector output and an output coupled to an output of the read-out amplifier, the integrator means operative to integrate output current being generated by the photovoltaic detector while the first switching means is in a high impedance state; and active load means coupled to the integrator means output, operative to provide a self-calibrated current sink for current output by the integrator means enabling the integrator means to maintain a substantially constant bias potential at the detector while the first switching means is in the high impedance state.

Claim 3

The amplifier of claim 1 wherein the integrator means comprises: an output driver amplifier for producing an output signal at an output terminal related to a signal presented to an input control terminal and including a feedback capacitor coupled between a driver output and the input control terminal, with the driver output terminal coupled to the integrator means output and the input control terminal coupled to the integrator means input.

Claim 4

The amplifier of claim 1 wherein the active load means comprises: an active electronic device for presenting an impedance between first and second device output terminals which is variable in accordance with a signal presented to a device input control terminal; a feedback capacitor coupled between one of the device output terminals and the input control terminal; and a second switching means coupling, in a low impedance state, the other one of the device output terminals to the input control terminal.

Claim 5

A read-out amplifier for an infrared detecting photovoltaic detector having a first electrode coupled to a first source of first bias potential and a second electrode coupled to an input of the read-out amplifier comprising: a first electronic switch having first and second output terminals and an input terminal, the first output terminal coupled to the read-out amplifier input, the second output terminal coupled to a source of second bias potential, and the input terminal coupled for receipt of a first reset signal, the first switch operative on receipt of the first reset signal to assume a low impedance state between its first and second output terminals; a driver amplifier having an input coupled to the read-out amplifier input and including a feedback capacitor coupled between the driver amplifier input and a driver amplifier output which is coupled to a read-out amplifier output, the driver amplifier operative to integrate current generated by the photovoltaic detector over a time interval during which the first reset signal is not present; and an active self-calibrating load including variable impedance means having a first output terminal coupled to the driver amplifier output, a second output terminal coupled to a source of third bias potential, and a control input terminal, a second electronic switch having a first output terminal coupled to the first output terminal of the variable impedance means, a second output terminal coupled to the control input terminal of the variable impedance means, and an input terminal coupled for receipt of a second reset signal, the second switch means operative on receipt of the second reset signal to assume a low impedance state between its first and second output terminals, and an autozero feedback capacitor coupled between the control input and second output terminals of the variable impedance means.

Claim 6

A read-out amplifier for an infrared detecting photovoltaic detector having a first electrode coupled to a first source of first bias potential and a second electrode coupled to an input of the read-out amplifier comprising: a first electronic switch having first and second output terminals and an input terminal, the first output terminal coupled to the read-out amplifier input, the second output terminal coupled to a source of second bias potential, and the input terminal coupled for receipt of a first reset signal, the first switch operative on receipt of the first reset signal to assume a low impedance state between its first and second output terminals; a driver amplifier having an input coupled to the read-out amplifier input and including a feedback capacitor coupled between the driver amplifier input and a driver amplifier output which is coupled to a read-out amplifier output, the driver amplifier operative to integrate current generated by the photovoltaic detector over a time interval during which the first reset signal is not present; and an active self-calibrating load including variable impedance means having a first output terminal coupled to the driver amplifier output, a second output terminal coupled to a source of third bias potential, and a control input terminal, a second electronic switch having a first output terminal coupled to the first output terminal of the variable impedance means, a second output terminal coupled to the control input terminal of the variable impedance means, and an input terminal coupled for receipt of a second reset signal, the second switch means operative on receipt of the second reset signal to assume a low impedance state between its first and second output terminals, and an autozero feedback capacitor coupled between the control input and second output terminals of the variable impedance means.

Claim 7

The read-out amplifier of claim 4 wherein: the first electronic switch comprises a first field effect transistor with a source electrode serving as the first output terminal, a drain electrode serving as the second output terminal and a gate electrode serving as the input terminal of the first electronic switch; the capacitive driver amplifier includes a second field effect transistor with a source electrode coupled to a fourth bias potential, a gate electrode serving as the driver amplifier input and a drain electrode serving as the driver amplifier output; the variable impedance means of the active load comprises a third field effect transistor with a drain electrode serving as the first output terminal, a source electrode serving as the second output terminal, and a gate electrode serving as a control input terminal of the variable impedance means; and the second electronic switch comprises a fourth field effect transistor with a drain electrode serving as the first output terminal, a source electrode serving as the second output terminal, and a gate electrode serving as the input terminal of the second electronic switch.

Claim 8

The read-out amplifier of claim 5 wherein the first and second field effect transistors comprise metal-oxide-silicon devices (MOSFETs) of PMOS type.

Claim 9

The read-out amplifier of claim 5 wherein the third and fourth field effect transistors comprise metal-oxide-silicon devices (MOSFETs) of NMOS type.

Claim 10

The read-out amplifier of claim 5 wherein the first, second, third and fourth field effect transistors comprise metal-oxide-silicon devices (MOSFETs).

Claim 11

The read-out amplifier of claim 8 wherein the second MOSFET further comprises a cascode gate electrode coupled to a source of fifth bias potential and operative to increase open loop gain of the capacitive driver amplifier.

Claim 12

The read-out amplifier of claim 8 wherein the second and third MOSFETs are selected such that the transconductance of the second MOSFET substantially exceeds the transconductance of the third MOSFET.