| US 7,567,125 B2 | ||
| Differential amplifier with multiple signal gains and wide dynamic range | ||
| Kenneth J. Carroll, Los Altos, Calif. (US) | ||
| Assigned to National Semiconductor Corporation, Santa Clara, Calif. (US) | ||
| Filed on May 15, 2007, as Appl. No. 11/748,950. | ||
| Prior Publication US 2008/0284514 A1, Nov. 20, 2008 | ||
| Int. Cl. H03F 3/45 (2006.01) | ||
| U.S. Cl. 330—254 [330/253] | 11 Claims |
| 1. An apparatus including a differential amplifier with multiple signal gains for amplifying a differential input signal over
a wide dynamic range, comprising:
differential input electrodes to convey a differential input signal;
differential output electrodes to convey a differential output signal;
first differential amplifier circuitry having a first signal gain and coupled between said differential input and output electrodes
to receive at least a first portion of said differential input signal and provide a first portion of said differential output
signal, and including
a first differential amplifier sub-circuit to receive said at least said first portion of said differential input signal and
a first tail current, and provide said first portion of said differential output signal in relation to said first signal gain,
and
a first bias sub-circuit coupled to said first differential amplifier sub-circuit to provide said first tail current; and
second differential amplifier circuitry having a second signal gain lower than said first signal gain and coupled between
said differential input and output electrodes to receive at least a second portion of said differential input signal and provide
a second portion of said differential output signal, and including
a second differential amplifier sub-circuit to receive said at least said second portion of said differential input signal
and a second tail current, provide said second portion of said differential output signal in relation to said second signal
gain, and
a second bias sub-circuit coupled to said second differential amplifier sub-circuit to provide said second tail current;
wherein, over a predetermined range of values of said differential input signal, a ratio of said differential output signal
to said differential input signal varies in relation to a continuous combination of said first and second signal gains.
|