Alasdair G Alexander

US Patent:

8390374, Mar 5, 2013

Filed:

Jan 25, 2011

Appl. No.:

13/013666

Inventors:

Alasdair Gordon Alexander - Andover MA, US
David James Plourde - Dracut MA, US
Matthew Nathan Duff - Somerville MA, US

Assignee:

Analog Devices, Inc. - Norwood MA

International Classification:

H03F 3/45

US Classification:

330 69, 330 85, 330147

Abstract:

Apparatus and methods reduce the likelihood of amplifier saturation due to propagated DC offsets, and reduce the recover from saturated stated when such saturation occurs. Advantageously, these attributes are beneficial for monitoring of bioelectric signals. A circuit uses an instrumentation amplifier connected as a high pass filter to attenuate large DC offsets and amplify small signals. The circuit can include an instrumentation amplifier electrically coupled with a first feedback circuit including at least one resistor and a second feedback circuit including an op-amp. The feedback circuit can also include a low-pass filter. The op-amp in the second feedback circuit can be configured as a non-inverting amplifier, an inverting amplifier, and/or an integrator circuit. Alternatively, the circuit can include an instrumentation amplifier with one feedback circuit including at least one resistor, and a coupling capacitor electrically coupled with a reference voltage.

US Patent:

8624668, Jan 7, 2014

Filed:

Dec 14, 2011

Appl. No.:

13/325750

Inventors:

Quan Wan - Belmont MA, US
Alasdair G. Alexander - Andover MA, US

Assignee:

Analog Devices, Inc. - Norwood MA

International Classification:

H03F 1/02

US Classification:

330 9

Abstract:

An auto-zero amplifier includes a main amplifier for amplifying an input signal; the main amplifier receives an offset-correction signal for cancelling an offset at a first common-mode level of the input signal. At the first common-mode level, the offset-correction signal is based on a first value stored using a first offset-storage element. When a change is detected in the input common-mode from the first level to a second level, the first offset-storage element is switched out and a second offset-storage element, having a second value based on the second common-mode level, is switched in.

US Patent:

20070001758, Jan 4, 2007

Filed:

Jun 30, 2005

Appl. No.:

11/172186

Inventors:

Alasdair Alexander - Andover MA, US
Chau Tran - Malden MA, US

International Classification:

H03F 3/45

US Classification:

330069000

Abstract:

A multiple differential amplifier system and method for transconductance mismatch compensation which in a first phase connects to a differential switched input of a null amplifier, the differential signal input of the main amplifier, inverted, for compensating for offset errors and transconductance mismatches in the null amplifier; and storing in a null storage device connected to an auxiliary input of the null amplifier the output of the null amplifier representing the compensation for the offset error and transconductance mismatch of the null amplifier; and in a second phase connecting the differential switched input of the null amplifier to the differential feedback input of the main amplifier and storing in the main storage device connected to an auxiliary input of the main amplifier the output of the null amplifier representing the compensation for the main amplifier offset error and transconductance mismatch.