High dynamic range variable gain amplifier
First Claim
Patent Images
1. A variable gain amplifier comprising:
- a transconductance input stage including at least one transistor having variable emitter degeneration, said transconductance input stage having a pair of differential voltage inputs for receiving a signal to be amplified and having a pair of differential current outputs;
at least one current amplifier coupled to said differential current outputs for amplifying said signal to be amplified; and
a control circuit, coupled to said transconductance input stage and said at least one current amplifier, for applying a control signal to said transconductance input stage and said at least one current amplifier, said control signal for exponentially varying a gain of said transconductance input stage and said at least one current amplifier in response to a linear variation in a control voltage;
wherein said transconductance input stage comprises;
a fixed transconductance input stage;
a variable transconductance input stage, said variable transconductance being varied by said control signal; and
a mode selection switch, coupled to said fixed transconductance input stage and said variable transconductance input stage, for alternately coupling said fixed transconductance input stage and said variable transconductance input stage to said at least one current amplifier in response to a mode selection signal.
1 Assignment
0 Petitions
Accused Products
Abstract
A multi-stage low power, high dynamic range variable gain amplifier comprises an input stage cascaded with one or more current amplifier stages, whereby the gain of each stage may be independently controlled. The input stage may be comprised of a variable transconductance amplifier using variable emitter degeneration. The current amplifier may be comprised of a differential Darlington amplifier coupled to a differential cascode amplifier. The transconductance amplifier converts an input voltage signal to a current signal. The variable gain amplifier is designed for efficient low power operation.
-
Citations
18 Claims
-
1. A variable gain amplifier comprising:
-
a transconductance input stage including at least one transistor having variable emitter degeneration, said transconductance input stage having a pair of differential voltage inputs for receiving a signal to be amplified and having a pair of differential current outputs; at least one current amplifier coupled to said differential current outputs for amplifying said signal to be amplified; and a control circuit, coupled to said transconductance input stage and said at least one current amplifier, for applying a control signal to said transconductance input stage and said at least one current amplifier, said control signal for exponentially varying a gain of said transconductance input stage and said at least one current amplifier in response to a linear variation in a control voltage; wherein said transconductance input stage comprises; a fixed transconductance input stage; a variable transconductance input stage, said variable transconductance being varied by said control signal; and a mode selection switch, coupled to said fixed transconductance input stage and said variable transconductance input stage, for alternately coupling said fixed transconductance input stage and said variable transconductance input stage to said at least one current amplifier in response to a mode selection signal. - View Dependent Claims (2, 3, 4, 5)
-
-
6. A variable gain amplifier comprising:
-
a transconductance input stage including at least one transistor having variable emitter degeneration, said transconductance input stage having a pair of differential voltage inputs for receiving a signal to be amplified and having a pair of differential current outputs; at least one current amplifier coupled to said differential current outputs for amplifying said signal to be amplified; and a control circuit, coupled to said transconductance input stage and said at least one current amplifier, for applying a control signal to said transconductance input stage and said at least one current amplifier, said control signal for exponentially varying a gain of said transconductance input stage and said at least one current amplifier in response to a linear variation in a control voltage, wherein said at least one current amplifier comprises; a differential Darlington amplifier having resistive shunt-series feedback; a differential cascode amplifier, coupled to said differential Darlington amplifier as a translinear loop; and a tail current generator, coupled to said control circuit, said differential Darlington amplifier, and said differential cascode amplifier, said tail current generator for generating a differential pair of tail currents whereby a gain of said current amplifier is proportional to a ratio of said differential pair of tail currents. - View Dependent Claims (7)
-
-
8. An amplifier for processing an input signal comprising:
-
an input stage including a transconductance amplifier having variable transconductance; a Gilbert cell attenuator coupled to said transconductance amplifier; a current amplifier, coupled to said input stage; and means for applying a linearly adjusted control voltage to said current amplifier to exponentially vary the gain of said amplifier as a function of the applied control voltage. - View Dependent Claims (9, 10)
-
-
11. An amplifier for processing an input signal comprising:
-
an input stage including a transconductance amplifier having variable transconductance; a transconductance amplifier bias control circuit coupled to said transconductance amplifier; a current amplifier, coupled to said input stage; and means for applying a linearly adjusted control voltage to said current amplifier to exponentially vary the gain of said amplifier as a function of the applied control voltage, wherein said transconductance bias control circuit further comprises; an exponential function generator; a first operational amplifier circuit coupled to said exponential function generator; a second operational amplifier circuit coupled to said first operational amplifier circuit; and a current source coupled to said first operational amplifier circuit. - View Dependent Claims (12, 13, 14, 15)
-
-
16. A method of amplifying an input signal in an amplifier having a fixed transconductance input stage and a variable transconductance input stage, said fixed transconductance input stage and said variable transconductance input stage being coupled to a current amplifier via a mode selection switch, the method comprising the steps of:
-
applying an input signal to said fixed transconductance input stage and said variable transconductance input stage; and selectively applying an output of said fixed transconductance input stage or said variable transconductance input stage to said current amplifier in response to a mode selection signal. - View Dependent Claims (17, 18)
-
Specification