Voltage to current converters for use in an active filter and with a moise reduction circuit

Claim 2

A voltage to current converter, comprising: a first voltage to current converting circuit responsive to a positive input level and having a first pair of outputs; a second voltage to current converting circuit responsive to a negative input level and having a second pair of outputs; an input section for said two voltage to current converting circuits; a first multiplier including a first pair of diodes, each of which is respectively supplied with one of said first outputs and a first pair of emitter-common differential transistors whose base electrodes are respectively given a potential difference between said first pair of diodes; a second multiplier including a second pair of diodes, each of which is respectively supplied with one of said second outputs, and a second pair of emitter-common differential transistors whose base electrodes are respectively given a potential difference between said second pair of diodes; and means for detecting output currents of said first and second multipliers.

Claim 3

A noise reduction circuit, comprising: a variable high-pass filter responsive to an input signal; an adder for adding an output of the filter and said input signal; a high-frequency weighting circuit responsive to said output of said filter; and a level detector for detecting an output of the weighting circuit and producing an output to said filter, said variable high-pass filter including a voltage to current converter, which comprises: a first pair of differential transistors having first and second transistors whose emitter electrodes are connected to each other through a feedback resistance; a second pair of differential transistors having third and fourth transistors whose emitter electrodes are connected to each other through a feedback resistance; a first current source connected to the emitter electrode of said second transistor and a second current source connected to the emitter electrode of said fourth transistor; a first multiplier including a first pair of diodes which are respectively supplied with collector currents of the first pair of differential transistors and a first pair of emitter-common differential transistors whose base electrodes are respectively given a potential difference of said first pair of diodes; a second multiplier including a second pair of diodes which are respectively supplied with collector currents of said second pair of differential transistors and a second pair of emitter-common differential transistors whose base electrodes are respectively given a potential difference of the second pair of diodes; a current-mirror circuit for taking out a collector current difference of one transistor of each of said first and second multipliers; two resistances connected in series and having one end coupled to an input terminal, a junction of said two resistances being connected to a base electrode of one of the first pair of differential transistors; a condenser having one end connected to said input terminal and the other end connected to one of a collector electrode of the first multiplier; and a resistance externally provided at said voltage to current converter.

Claim 4

A noise reduction circuit, comprising: a variable high-pass filter responsive to an input signal; an adder for adding an output of the filter and said input signal; a high-frequency weighting circuit responsive to said output of said filter; and a level detector for detecting an output of the weighting circuit and producing an output to said filter, said variable high-pass filter including a voltage to current converter, which comprises: a first pair of differential transistors having first and second transistors whose emitter electrodes are connected to each other through a feedback resistance; a second pair of differential transistors having third and fourth transistors whose emitter electrodes are connected to each other through a feedback resistance; a first current source connected to the emitter electrode of said second transistor and a second current source connected to the emitter electrode of said fourth transistor; a first multiplier including a first pair of diodes which are respectively supplied with collector currents of the first pair of differential transistors and a first pair of emitter-common differential transistors whose base electrodes are respectively given a potential difference of said first pair of diodes; a second multiplier including a second pair of diodes which are respectively supplied with collector currents of said second pair of differential transistors and a second pair of emitter-common differential transistors whose base electrodes are respectively given a potential difference of the second pair of diodes; a current-mirror circuit for taking out a collector current difference of one transistor of each of said first and second multipliers; two resistances connected in series and having one end coupled to an input terminal, a junction of said two resistances being connected to a base electrode of one of the first pair of differential transistors; a condenser having one end connected to said input terminal and the other end connected to one of a collector electrode of the first multiplier; and a resistance externally provided at said voltage to current converter.

Claim 5

A voltage to current converter as claimed in claim 2, wherein said first voltage to current converting circuit includes a plurality of differential transistors having a first transistor and plural second transistors connected in parallel with each other, emitter electrodes of the first and second transistors being connected to each other through a first feedback resistance, and said second voltage to current converting circuit includes a plurality of a plurality of differential transistors having a third transistor and plural fourth transistors connected in parallel with each other, emitter electrodes of the third and fourth transistors being connected to each other through a second feedback resistance.

Claim 6

A voltage to current converter, comprising: a first pair of differential transistors having first and second transistors whose emitter electrodes are connected to each other through a feedback resistance; a second pair of differential transistors having third and fourth transistors whose emitter electrodes are connected to each other through a feedback resistance; a first current source connected to the emitter electrode of said second transistor and a second current source connected to the emitter electrode of said fourth transistor; a first multiplier including a first pair of diodes which are respectively supplied with collector currents of the first pair of differential transistors and a first pair of emitter-common differential transistors whose base electrodes are respectively given a potential difference of said first pair of diodes; a second multiplier including a second pair of diodes which are respectively supplied with collector currents of said second pair of differential transistors and a second pair of emitter-common differential transistors whose base electrodes are respectively given a potential difference of the second pair of diodes; and a current-mirror circuit for taking out a collector current difference of one transistor of each of said first and second multipliers.

Claim 7

A voltage to current converter, comprising: a first pair of differential transistors having first and second transistors whose emitter electrodes are connected to each other through a feedback resistance; a second pair of differential transistors having third and fourth transistors whose emitter electrodes are connected to each other through a feedback resistance; a first current source connected to the emitter electrode of said second transistor and a second current source connected to the emitter electrode of said fourth transistor; a first multiplier including a first pair of diodes which are respectively supplied with collector currents of the first pair of differential transistors and a first pair of emitter-common differential transistors whose base electrodes are respectively given a potential difference of said first pair of diodes; a second multiplier including a second pair of diodes which are respectively supplied with collector currents of said second pair of differential transistors and a second pair of emitter-common differential transistors whose base electrodes are respectively given a potential difference of the second pair of diodes; and a current-mirror circuit for taking out a collector current difference of one transistor of each of said first and second multipliers.

Claim 8

A voltage to current converter as claimed in claim 4, wherein said first pair of differential transistors operate in response to an input level larger than a predetermined level and said second pair of differential transistors operate in response to the input level equal to or less than said predetermined level.

Claim 9

A voltage to current converter as claimed in claim 4, further comprising: two resistances connected in series and having a junction coupled to an output terminal therebetween; a current source connected to one end of said resistances connected in series; and an emitter follower transistor whose emitter electrode is connected to the other end of said resistances connected in series, a base electrode of one of said first pair of differential transistors being connected to a junction between said current source and said one end of the resistances connected in series, and a base electrode of one of said second pair of differential transistors being connected to a junction between the emitter electrode of said emitter follower transistor and said the other end of said resistances connected in series.

Claim 10

An active filter using a voltage to current converter, which comprises: a first pair of differential transistors having first and second transistors whose emitter electrodes are connected to each other through a feedback resistance; a second pair of differential transistors having third and fourth transistors whose emitter electrodes are connected to each other through a feedback resistance; a first current source connected to the emitter electrode of said second transistor and a second current source connected to the emitter electrode of said fourth transistor; a first multiplier including a first pair of diodes which are respectively supplied with collector currents of the first pair of differential transistors and a first pair of emitter-common differential transistors whose base electrodes are respectively given a potential difference of said first pair of diodes; a second multiplier including a second pair of diodes which are respectively supplied with collector currents of said second pair of differential transistors and a second pair of emitter-common differential transistors whose base electrodes are respectively given a potential difference of the second pair of diodes; a current-mirror circuit for taking out a collector current difference of one transistor of each of said first and second multipliers; two resistances connected in series and having one end coupled to an input terminal, a junction of said two resistances being connected to a base electrode of one of the first pair of differential transistors; a condenser having one end connected to said input terminal and the other end connected to one of a collector electrode of the first multiplier; and a resistance externally provided at said voltage to current converter.

Claim 11

An active filter using a voltage to current converter, which comprises: a first pair of differential transistors having first and second transistors whose emitter electrodes are connected to each other through a feedback resistance; a second pair of differential transistors having third and fourth transistors whose emitter electrodes are connected to each other through a feedback resistance; a first current source connected to the emitter electrode of said second transistor and a second current source connected to the emitter electrode of said fourth transistor; a first multiplier including a first pair of diodes which are respectively supplied with collector currents of the first pair of differential transistors and a first pair of emitter-common differential transistors whose base electrodes are respectively given a potential difference of said first pair of diodes; a second multiplier including a second pair of diodes which are respectively supplied with collector currents of said second pair of differential transistors and a second pair of emitter-common differential transistors whose base electrodes are respectively given a potential difference of the second pair of diodes; a current-mirror circuit for taking out a collector current difference of one transistor of each of said first and second multipliers; two resistances connected in series and having one end coupled to an input terminal, a junction of said two resistances being connected to a base electrode of one of the first pair of differential transistors; a condenser having one end connected to said input terminal and the other end connected to one of a collector electrode of the first multiplier; and a resistance externally provided at said voltage to current converter.