Claims
- 1. A circuit for providing an output signal of controllable amplitude responsive to the data contained in at least one externally-provided digital control signal, comprising:
- feedback oscillator means for providing a periodic output waveform having a selected frequency and a variable amplitude responsive to the magnitude of a first voltage applied to a control input of said oscillator means;
- a circuit output terminal at which appears the circuit output signal with said oscillator means output waveform frequency and said controllable amplitude;
- first and second sources of circuit operating potential;
- a plurality of resistance elements each having a first terminal thereof connected in parallel to the first terminals of all other resistance elements, and each having a second terminal; said resistance element second terminal being individually connectable to one of said first and second sources of circuit operating potential responsive to said digital control signal data; and
- means connected between said resistance element first terminals and said oscillator means control input for supplying to said oscillator means control input said first voltage at an amplitude established by the particular combination of said resistance element second terminals connected respectively to said first and second operating potentials.
- 2. The circuit of claim 1, wherein said feedback oscillator means comprises: a differential amplifier receiving said first and second operating potentials and having an inverting input, a non-inverting input and an output; a capacitive element coupled between said inverting input and said first operating potential; first and second feedback resistance elements coupled between said differential amplifier output and one of inverting and non-inverting inputs, respectively; an electrical resistance connected between said non-inverting input and said first operating potential; and first and second series-connected resistance elements connected between said non-inverting input and said output; the junction between series-connected resistance elements forming said feedback oscillator means control input.
- 3. The circuit of as set forth in claim 2, wherein said oscillator means output waveform is a substantially square waveform.
- 4. The circuit as set forth in claim 3, wherein said electrical resistance and said second feedback resistance element are of substantially equal magnitudes to cause said oscillator means to provide said substantially square output waveform.
- 5. The circuit as set forth in claim 1 or 2, wherein said first voltage supplying means comprises: another differential amplifier having a non-inverting input connected to said resistance element first terminals, an inverting input and an output; a gain-setting resistance connected between said another differential amplifier input and said first operating potential; a transistor having a collector electrode connected to said second operating potential, a base electrode connected to said another differential amplifier output, and an emitter electrode which is said converting means output and is connected to said oscillator means control input; and a feedback resistance element connected between said differential amplifier inverting input and said transistor emitter electrode.
- 6. The circuit is set forth in claim 5, wherein said first voltage supplying means further comprises: a diode having an anode connected to said resistance element first terminals and a cathode; and an additional resistance element connected between the diode cathode and said first operating potential.
- 7. The circuit of claim 6, wherein said first voltage supplying means further comprises another diode in series with said feedback resistance element.
- 8. The circuit of claim 7, wherein said another diode is selected to temperature compensate for the effects of said first diode.
- 9. The circuit of claim 5, further comprising a capacitance element connected between said another differential amplifier inverting input and said converting means output.
- 10. The circuit of claim 5, further comprising a low pass filter network connected between said another differential amplifier output and said second operating potential.
- 11. The circuit of claim 1, further amplifier comprising amplifier means for providing said oscillator means output waveform to said circuit output terminal with a varying amplitude responsive to the variable amplitude waveform of said oscillator means.
- 12. The circuit of claim 11, wherein said amplifier means comprises: a complementary-symmetry pair of output transistors, each having base and emitter electrodes respectively connected to the respective base and emitter electrodes of the other transistor, and each having a collector electrode connected to a different one of said first and second operating potentials; a driver transistor having a collector electrode connected to said output transistor base electrodes, an emitter electrode connected to said first operating potential and a base electrode receiving said oscillator means output; waveform; and a capacitive element for coupling the output transistor emitter electrodes to said circuit output terminal.
- 13. The circuit of claim 12, wherein said amplifier means further comprises: a resistance element coupling said oscillator means output waveform to said driver transistor base electrode; and a capacitive element in electrical parallel connection across said coupling resistance element.
- 14. The circuit of claim 12, wherein said amplifier means further comprises means for providing a current, to said output transistor base electrodes, of magnitude responsive to the magnitude of said first voltage.
- 15. The circuit of claim 14, wherein said current providing means comprises: first and second transistors, each having a base electrode connected to each other and to a collector electrode of the first transistor, the collector electrode of said second transistor being connected to said output transistor base electrodes, and each having an emitter electrode; first and second resistance elements each having a first terminal connected to one of said first and second transistor emitter electrodes and having a second terminal receiving said first voltage; and another resistance element coupled between said first and second transistor base electrodes and said first operating potential.
- 16. The circuit of claim 15, wherein said digital control signal is provided from a plurality of independently-controllable outputs of microcomputer.
- 17. The circuit of claim 16, wherein said oscillator means is adapted for providing a pulsed periodic output waveform at said selected frequency, responsive to a second voltage applied to said oscillator means.
- 18. The circuit of claim 17, wherein another independently controlled output of said microcomputer provides said second voltage as a selected one of said first and second operating potentials; said oscillator means pulsed output waveform being provided by changing a circuit parameter of said oscillator means responsive to a first one of said first and second operating potentials being provided at said another microcomputer output; said oscillator means providing a substantially square output waveform when said another microcomputer output provides the remaining one of said first and second operating potentials.
- 19. The circuit of claim 1, wherein said oscillator means is adapted for providing a periodic pulse waveform at said selected frequency, responsive to a second voltage applied to said oscillator means.
Parent Case Info
This is a divisional of applicaion Ser. No. 267,274, filed May 26, 1981, now U.S. Pat. No. 4,414,501.
US Referenced Citations (5)
Divisions (1)
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Number |
Date |
Country |
Parent |
267274 |
May 1981 |
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