Programmable low noise CMOS differentially voltage controlled logarithmic attenuator and method

A logarithmic attenuator circuit comprising;

• (a) a first resistive attenuator including
• I. a first input conductor and a first output conductor,
• ii. a first single series resistive element connected between the first input conductor and the first output conductor, and
• iii a first group of successive parallel controllable resistive elements each having a control terminal and each also having a first terminal connected to the first output conductor;
• (b) a second resistive attenuator including
• I. a second input conductor and a second output conductor,
• ii. a second single series resistive element connected between the second input conductor and the second output conductor, and
• iii. a second group of successive parallel controllable resistive elements each having a control terminal and each also having a first terminal connected to the second output conductor;
• (c) a control circuit producing a plurality of successive gradually increasing and then leveling off analog control signals on the control terminals of successive controllable resistive elements of the first and second groups, respectively, so as to change the controllable resistive elements from being at the edge of condition to being fully on in response to gradual linear changing of an analog gain control signal from a first value to a second value, wherein fully on resistances of the successive parallel controllable resistive elements decrease progressively.

A logarithmic gain circuit comprising:

• (a) an attenuator including
• I. an input conductor and an output conductor,
• ii. a single series impedance element connected between the input conductor and the output conductor, and
• iii. a plurality of successive parallel controllable impedance elements each having a control terminal and each also having a first terminal connected to the output conductor,
• (b) an analog control circuit producing a plurality of successive control signals on the control terminals of successive controllable impedance elements, respectively, so as to change the controllable impedance elements from being at the edge of conduction to being fully on in response to linear changing of an analog gain control signal from a first value to a second value, a magnitude of each control signal gradually increasing and then leveling off at a predetermined value, wherein fully on impedance of the successive parallel controllable impedance elements decrease progressively.

A logarithmic gain circuit comprising:

• (a) a resistive attenuator including
• I. an input conductor and an output conductor,
• ii a single series resistive element connected in series between the input conductor and the output conductor, and
• iii. a plurality of parallel successive resistive elements each having a first terminal connected to the output conductor, each of the parallel resistive elements including an electrically controllable resistive element having a control terminal operative to control the resistance thereof, each of the parallel resistive elements including a second terminal coupled to a common conductor;
• and
• (b) an analog control circuit producing a plurality of successive piecewise-linear gradually changing analog control voltage signals on the control terminals of successive electrically controllable resistive elements, respectively, so as to change the electrically controllable resistive elements form being at the edge of conduction to being fully on in response to gradual changing of an analog gain control signal from a first value to a second value, wherein fully on resistances of the electrically controllable resistive elements of the successive parallel resistive elements decrease progressively.

A logarithmic amplifier circuit comprising:

• (a) an operational amplifier having an inverting input, a non-inverting input, and an output;
• (b) a logarithmic attenuator having an input coupled to the output of the operational amplifier and an output coupled to the inverting input of the operational amplifier, the logarithmic attenuator including
• (1) a resistive attenuator including
• I. an input conductor and an output conductor,
• ii. a single series resistive element connected between the input conductor and the output conductor, and
• iii. a plurality of successive parallel resistive elements each having a first terminal connected to the output conductor, each of the successive parallel resistive elements including an electrically controllable resistive element having a control terminal operative to control the resistance thereof, each of the parallel resistive elements including a second terminal coupled to a common conductor;
• and
• (2) an analog control circuit producing a plurality of successive piecewise-linear gradually changing analog control voltage signals on the control terminals of successive electrically controllable resistive elements, respectively, so as to change the electrically controllable resistive element from being at the edge of conduction to being fully on in response to gradual changing of an analog gain control signal from a first value to a second value, wherein fully on resistances of the electrically controllable resistive elements of the successive parallel resistive elements decrease progressively.

A logarithmic amplifier circuit comprising:

• (a) first and second amplifiers each having an input and an output;
• (b) a logarithmic attenuator having an input coupled to the output of the first amplifier and an output coupled to the input of the second amplifier, the logarithmic attenuator including
• (1) a resistive attenuator including
• I. an input conductor and an output conductor,
• ii. a single series resistive element connected between the input conductor and the output conductor, and
• iii. a plurality of successive parallel resistive elements each having a first terminal connected to the output conductor, each of the parallel resistive elements including an electrically controllable resistive element having a control terminal operative to control the resistance thereof, each of the parallel resistive elements including a second terminal coupled to a common conductor;
• and
• (2) an analog control circuit producing a plurality of successive piecewise-linear gradually changing analog control voltage signals on the control terminals of successive electrically controllable resistive elements, respectively, so as to change the electrically controllable resistive elements from being at the edge of conduction to being fully on in response to gradual changing of an analog gain control signal from a first value to a second value, wherein fully on resistance of the electrically controllable resistive elements of the successive parallel resistive elements.

A programmable logarithmic attenuator circuit comprising:

• (a) a resistive attenuator including
• I. an input conductor and an output conductor,
• ii. a single series resistive element connected between the input conductor and the output conductor,
• iii. a first group of parallel electrically controllable resistive elements each having a control terminal and each also having a first terminal connected to the output conductor, and
• iv. a second group of parallel electrically controllable resistive elements each having a first terminal connected to the output conductor;
• (b) a first gain control conductor coupled to the control terminal of each of the electrically controllable resistive elements of the first group, and a second gain control conductor coupled to the control terminal of each of the electrically controllable resistive elements of the second group, to control a gain of the programmable logarithmic attenuator circuit by turning on any selected combination of the electrically controllable resistive element of the first group, or the electrically controllable resistive elements of the second group;
• and
• (c) a control circuit producing a plurality of successive gradually increasing and then leveling off analog control signals on the control terminals of successive ones of the electrically controllable resistive elements, respectively, so as to change the electrically controllable resistive elements from being at the edge of conduction to being fully on in response to gradual linear changing of an analog gain control signal from a first value to a second value, wherein fully on resistances of the successive electrically controllable resistive elements decrease progressively.

A differential logarithmic attenuator circuit comprising:

• (a) a first resistive attenuator including
• I. a first input conductor and a first output conductor,
• ii. a single series resistive element connected between the first input conductor and the first output conductor, and
• iii. a first group of parallel electrically controllable resistive elements each having a control terminal and each also having a first terminal connected to the output conductor;
• (b) a second resistive attenuator including
• I. a second input conductor and a second output conductor,
• ii. a single series resistive element connected between the second input conductor and the second output conductor, and
• iii. a second group of parallel electrically controllable resistive elements each having a control terminal aid each also having a first terminal connected to the second output conductor;
• (c) a control circuit producing a plurality of successive gradually increasing and then leveling off analog control signals on the control terminals of successive ones of the electrically controllable resistive elements, respectively, so as to change the electrically controllable resistive elements from being at the edge of conduction to being fully on in response to gradual linear chancing of an analog gain control signal from a first value to a second value, wherein fully on resistance of the successive electrically controllable resistive elements decrease progressively.

A method of operating a circuit to provide programmable logarithmically controlled attenuation, comprising:

• (a) providing a resistive attenuator including an input conductor and an output conductor, a single series resistive element connected between the input conductor and the output conductor, a first group of parallel electrically controllable resistive elements each having a first terminal connected to the output conductor, each having a control terminal, and a second group of parallel her electrically controllable resistive elements each having a first terminal connected to the output conductor, each having a control terminal;
• (b) applying a first gain control signal to the control terminal of each of the electrically controllable resistive elements of the first group, and a second gain control signal to the control terminal of each of the electrically controllable resistive elements of the second group to select the attenuation by turning on to a predetermine degree any selected combination of the electrically controllable resistive elements of the first group, the electrically controllable resistive elements of the second group;
• and
• (c) producing a plurality of successive gradually increasing and then leveling off analog control signals on the control terminals of successive ones of the electrically controllable resistive elements, respectively, so as to change the controllable resistive elements from being at the edge of conduction to being fully on in response to gradual linear changing of an analog gain control signal from a first value to a second value.