US 4,731,590 AGranted

Circuits with multiple controlled gain elements

AssigneeAmerican Telephone and Telegraph Company, AT&T Bell Laboratories

InventorVeikko R. Saari

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Abstract

An automatic cable equalizer (10) is implemented in CMOS technology with a reduced requirement for off-chip components. A continuously-variable gain control resistor (28) of an AGC circuit (12) in a gain section and two additional continuously-variable gain control resistors (76, 82) in a shaping section (16) of the equalizer are driven by monotonically related control voltages (V.sub.H1, V.sub.H2, V.sub.L1, V.sub.L2) which are derived from a single feedback loop section (16) by the use of an inverter (102) and a pair of inverters with voltage offset (104, 105). An arrangement is disclosed for realizing a detector (96) and a filter (98) of the gain control feedback section. Another arrangement (134) is disclosed for realizing the inverter (102) and the inverters with voltage offset (104, 105). A third arrangement (154) is disclosed for realizing gain control resistor networks which include the gain control resistors.

Claims5

Dependent claims

Gain control apparatus having an input node adapted to be supplied with an input signal to be controlled and an output node for yielding an output signal representative of a gain controlled version of the input signal comprising:

a first gain control circuit including a first continuously controllable variable resistance network having control nodes for controlling the gain of said first gain control circuit;
a signal shaping section including a second continuously controllable resistance network having second control nodes for controllably varying the amplitude of an applied signal, said shaping section and said first gain control circuit being connected in tandem;
and
a single control-loop definition network means supplied with the output signal from the gain control apparatus output node for generating a first plurality of control signals which are monotonically related and are supplied to said first and second control nodes, said first and second continuously controllable resistance networks being responsive to said first plurality of control signals so that amplitude variation of said input signal is control said second continuously controllable resistance network for input signal amplitude values less than a predetermined value and by said first gain control circuit for input signal amplitude values greater than said predetermined value.

1 more element

Dependencies are inferred from the claim text.