US 5,710,527 A · Complementary voltage to current conversion for voltage controlled oscillator

Abstract

A voltage controlled oscillator has a linear voltage to current characteristic from ground to the supply voltage. This oscillator includes a voltage to current converter which employs two output current paths. The first output current path includes an N-type MOSFET whose gate receives the input voltage. A level shifter circuit receives the input voltage and provides an output voltage shifted up by an amount equal to the input threshold voltage of an N-type MOSFET. A clamp circuit connected to the output of the level shifter circuit prevents this output voltage from becoming greater than a voltage equal to the sum of the input threshold voltage of an N-type MOSFET and the input threshold voltage of a P-type MOSFET. The gate of the second N-type MOSFET receives the output of the level shifter as clamped by the clamp circuit. A current mirror circuit supplies a current control to ring oscillator, whose frequency depends upon the current. A second embodiment includes a new ring oscillator. The voltage to current converter supplies two pair of N-type MOSFETs. The ring oscillator includes two phase control circuits, one for opposite phases of the oscillatory output.

Claims25

Dependent claims

A voltage to current circuit comprising:

a first N-type MOSFET having a gate supplied with an input voltage;
a level shifter circuit having an input receiving said input voltage and an output supplying an output voltage which corresponds to said input voltage shifted up by a first predetermined amount;
a clamp circuit connected to said output of said level shifter circuit, said clamp circuit preventing said output voltage from becoming greater than a second predetermined voltage, said second predetermined voltage being greater than said first predetermined voltage;
a second N-type MOSFET having a gate supplied with said output voltage of said level shifter as clamped by said clamp circuit;
and
a current mirror circuit having a current input supplied by a source-drain current of said first N-type MOSFET and a source-drain current of said second N-type MOSFET and a current output corresponding to said current input, said current output of said current mirror circuit supplying a current output of said voltage to current circuit.

3 more elements

A voltage controlled oscillator circuit comprising:

a first N-type MOSFET having a gate supplied with an input voltage;
a level shifter circuit having an input receiving said input voltage and an output supplying an output voltage which corresponds to said input voltage shifted up by a first predetermined amount;
a clamp circuit connected to said output of said level shifter circuit, said clamp circuit preventing said output voltage from becoming greater than a second predetermined voltage, said second predetermined voltage being greater than said first predetermined voltage;
a second N-type MOSFET having a gate supplied with said output voltage of said level shifter as clamped by said clamp circuit;
a current mirror circuit having a current input supplied by a source-drain current of said first N-type MOSFET and a source-drain current of said second N-type MOSFET and a current output corresponding to said current input;
and
a ring oscillator producing an oscillating signal at an output, said ring oscillator receiving said current output of said current mirror circuit and oscillating at a frequency determined by said current output of said current mirror.

4 more elements

A voltage controlled oscillator circuit comprising:

a first N-type MOSFET having a gate supplied with an input voltage;
a second N-type MOSFET having a gate supplied with an input voltage;
a level shifter circuit having an input receiving said input voltage and an output supplying an output voltage which corresponds to said input voltage shifted up by a first predetermined amount;
a clamp circuit connected to said output of said level shifter circuit, said clamp circuit preventing said output voltage from becoming greater than a second predetermined voltage, said second predetermined voltage being greater than said first predetermined voltage;
a third of N-type MOSFET having a gate supplied with said output voltage of said level shifter as clamped by said clamp circuit;
a fourth of N-type MOSFET having a gate supplied with said output voltage of said level shifter as clamped by said clamp circuit;
a ring oscillator producing an oscillating signal at an output, said ring oscillator including
a first phase control circuit having a current input supplied by a source-drain current of said first N-type MOSFET and a source-drain current of said third N-type MOSFET, said first phase control circuit controlling a first phase of said oscillating signal to have a length corresponding to a sum of said source-drain current of said first N-type MOSFET and said source-drain current of said third N-type MOSFET, and
a second phase control circuit having a current input supplied by a source-drain current of said second N-type MOSFET and a source-drain current of said fourth N-type MOSFET, said second phase control circuit controlling a second phase of said oscillating signal opposite to said first phase of said oscillating signal to have a length corresponding to a sum of said source-drain current of said second N-type MOSFET and
said source-drain current of said fourth N-type MOSFET, said first and second phase control circuits coupled together to operate in opposite phase.

7 more elements

Dependencies are inferred from the claim text.

Complementary voltage to current conversion for voltage controlled oscillator

Life of this patent

Complementary voltage to current conversion for voltage controlled oscillator

Life of this patent

Abstract

Claims25