# US 4,400,668 A · Period proportional two-phase voltage controlled oscillator

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- Number: US 4,400,668 A
- Document ID: US4400668A
- Status: Granted
- Kind: A
- Application number: 06/275,356
- Filed: 1981-06-19
- Granted: 1983-08-23
- Earliest claimed: 1980-06-24
- Assignees: Baldwin Piano & Organ Company
- Inventors: Dale M. Uetrecht
- Web page: https://patentgrep.com/patent/US4400668A

## CPC

- G10H 1/043: Continuous modulation
- H03K 3/03: Astable circuits
- H03K 7/06: Frequency or rate modulation, i.e. PFM or PRM
- Y10S 331/03: Logic gate active element oscillator
- G10H: ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
- H03K: PULSE TECHNIQUE (measuring pulse characteristics G01R; modulating sinusoidal oscillations with pulses H03C; transmission of digital information H04L; discriminator circuits detecting phase difference between two signals by counting or integrating cycles of oscillation H03D3/04; automatic control, starting, synchronisation or stabilisation of generators of electronic oscillations or pulses where the type of generator is irrelevant or unspecified H03L; coding, decoding or code conversion, in general H03M)
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

A two-phase, period-proportional voltage-controlled oscillator circuit is provided for clocking an analog delay line which can be used, for example, in an electronic musical instrument. The voltage-controlled oscillator circuit provides two clock output signals of opposite phase and having a period directly proportional to the control voltage, i.e., the frequency of the two clock signals is inversely proportional to the control voltage. Since the delay provided by the analog delay line is directly proportional to the period of the clock signals, the delay is directly proportional to the control voltage thereby eliminating a source of distortion in a delay modulation system.

## Claims

### Claim 1

A period-proportional voltage-controlled oscillator apparatus comprising:
a transistor;
bias means connected to a first source of operating potential for biasing the emitter of said transistor;
means for connecting the emitter of said transistor to a source of time varying modulation control voltage;
capacitive means connected between the base of said transistor and the collector of said transistor;
first impedance means connecting the base of said transistor to a second source of operating potential;
second impedance means connecting the collector of said transistor to the second source of operating potential;
first inverter means having its input connected to the collector of said transistor for providing a first output signal;
second inverter means having its input connected to the output of said first inverter means for providing a second output signal; and
diode means connecting the output of said second inverter means to the base of said transistor;
whereby when the output of said second inverter means is in a first state, said diode is forward biased and said transistor is in the off state thereby causing said capacitive means to discharge through said second impedance means and the voltage level at the collector of said transistor to decrease until the threshold voltage of said first inverter means is reached, at which time the output of said first inverter means switches from a second state to the first state thereby causing the output of said second inverter means to switch from the first state to the second state, thereby in turn reverse biasing said diode and causing said transistor to switch to the on state, thereby further causing said capacitive means to charge through said first impedance means until the threshold voltage of said first inverter means is reached, at which time the output of said first inverter means again switches states and the cycle is repeated, and whereby the period of said first and second output signals is directly proportional to the amplitude of the modulation control voltage.

### Claim 2

A period-proportional voltage-controlled oscillator apparatus comprising:
a transistor;
bias means connected to a first source of operating potential for biasing the emitter of said transistor;
means for connecting the emitter of said transistor to a source of modulation control voltage;
a capacitor connected between the base of said transistor and the collector of said transistor;
a first resistor connecting the base of said transistor to a second source of operating potential;
a second resistor connecting the collector of said transistor to the second source of operating potential;
first inverter means having its input connected to the collector of said transistor for providing a first output signal;
second inverter means having its input connected to the output of said first inverter means for providing a second output signal; and
diode means connecting the output of said second inverter means to the base of said transistor, whereby said first and second output signals of the same frequency are provided at the output of said first and second inverter means, respectively, each alternating between first and second voltage levels and not overlapping for one of said first and second voltage levels.

### Claim 3 (depends on 2)

The apparatus as claimed in claim 2 wherein the period of said first and second output signals is directly proportional to the amplitude of a time varying modulation control voltage applied to the emitter of said transistor.