Bipolar transistor logarithmic converter with AC diode connection
AssigneeTexas Instruments Incorporated
InventorsMartijn Snoeij, Viola Schaffer
Life of this patent
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Abstract
A logarithmic converter circuit includes a converter input and a converter output. The circuit includes a first transistor which includes a control terminal, a first terminal coupled to the converter input, and a second terminal coupled to the converter output. The circuit includes a first operational amplifier which includes a first input coupled to the converter input, a second input coupled to a common potential, and an output coupled to the second terminal. The circuit includes a first capacitor coupled between the first terminal and the control terminal and includes a first resistor coupled between the control terminal and the common potential.
Claims20
A logarithmic converter circuit comprising:
- a converter input and a converter output;
- a first transistor having a control terminal, a first terminal coupled to the converter input, and a second terminal coupled to the converter output;
- a first operational amplifier having a first input coupled to the converter input, a second input coupled to a common potential, and an output coupled to the second terminal;
- a high-pass filter coupled to the converter input and the control terminal;
- and
- a buffer having an input coupled to the high-pass filter and an output coupled to the control terminal.
A logarithmic converter circuit comprising:
- a converter input and a converter output;
- a first transistor having a control terminal, a first terminal coupled to the converter input, and a second terminal coupled to the converter output;
- a first operational amplifier having a first input coupled to the converter input, a second input coupled to a common potential, and an output coupled to the second terminal;
- a high-pass filter coupled to the converter input and the control terminal, wherein the high-pass filter comprises:
- a first capacitor coupled between the first terminal and the control terminal;
- and
- a first resistor coupled between the control terminal and the common potential.
A logarithmic converter circuit comprising:
- a converter input and a converter output;
- a first transistor having a control terminal, a first terminal coupled to the converter input, and a second terminal coupled to the converter output;
- a first operational amplifier having a first input coupled to the converter input, a second input coupled to a common potential, and an output coupled to the second terminal;
- a high-pass filter coupled to the converter input and the control terminal;
- a resistor having a first terminal coupled to the first input of the first operational amplifier and having a second terminal;
- and
- an input current source having a first terminal coupled to the second terminal of the resistor and having a second terminal coupled to the common potential.
A logarithmic converter circuit comprising:
- a converter input and a converter output;
- a first transistor having a control terminal, a first terminal coupled to the converter input and a second terminal coupled to the converter output;
- a first operational amplifier having a first input coupled to the converter input, a second input coupled to a common potential, and an output coupled to the second terminal;
- a second operational amplifier having an output, a third input coupled to the control terminal, and a fourth input adapted to be coupled to a bias source;
- a first resistor coupled between the control terminal and the output of the second operational amplifier;
- and
- a first capacitor coupled between the first terminal and the first resistor.
A logarithmic converter circuit comprising:
- a converter input and a converter output;
- a first transistor having a base, a collector coupled to the converter input and an emitter coupled to the converter output;
- a first operational amplifier having an inverting input coupled to the converter input, a non-inverting input coupled to a common potential, and an output coupled to the converter output;
- a second operational amplifier having an output, an inverting input coupled to the base, and a non-inverting input adapted to be coupled to a bias voltage, the second operational amplifier operable to regulate a voltage at the base of the first transistor responsive to the bias voltage;
- a buffer having an input, and an output coupled to the base;
- and
- a high-pass filter having a first terminal coupled to the collector, a second terminal coupled to the input of the buffer, and a third terminal coupled to the output of the second operational amplifier, the high-pass filter operable to electrically couple the base to the collector if the input current has a high frequency and operable to electrically de-couple the base from the collector if the input current is a direct current (DC).
Dependencies are inferred from the claim text.