Wide-dynamic-range amplifier with a charge-pump load and energizing circuit

• US 5,212,456 A
• Filed: 09/03/1991
• Issued: 05/18/1993
• Est. Priority Date: 09/03/1991
• Status: Expired due to Term

• Current Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Original Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Inventors: Latham, Paul W. II, Kovalcik, Thomas J.
• Primary Examiner(s): Dzierzynski, Paul M.
• Assistant Examiner(s): DINH, TAN X
• Application Number:
  US07/753,483
• Time in Patent Office: 623 Days
• Field of Search: 330/261, 330/307, 330/253, 330/257, 307/296.2, 307/303.2
• US Class Current: 330/261
• CPC Class Codes: H03F 1/0261 with control of the polarisation voltage or current, e.g. gliding Class A
• CPC Class Codes: H03F 3/45076 characterised by the way of implementation of the active amplifying circuit in the differential amplifier
• CPC Class Codes: H03F 3/505 with field-effect devices

Abstract

An amplifier has a first stage employing a pair of differentially connected NMOS amplifier transistors, a second stage composed of a bipolar current mirror circuit and two charge pumps. Each charge pump may be a switching voltage multiplier circuit without the conventional output capacitor. The outputs of the two charge pumps are connected, respectively, to the collector of the current-mirror output transistor and to the commonly connected sources of the NMOS amplifier transistors. Each charge pump serves as both a pulse-voltage energizing source and a load to the amplifier. The amplifier is incorporated with a high-current NMOS transistor in an integrated circuit, wherein one differential input of the amplifier is connected to the source of the driver transistor at which an external load, e.g. a motor, may be connected. The output (collector) of the differential amplifier is connected to the gate of the NMOS driver transistor so that the load current through the driver transistor is held regulated to a value proportional to the input or reference voltage that is applied to the other input of the differential amplifier. The peak pulse voltage of each charge pump is greater than the DC supply voltage from which the driver transistor and the two charge pumps are energized so that the dynamic range of both the input control voltage and the amplifier output to the gate of the NMOS driver transistor is much greater than the DC supply voltage to the integrated circuit.

Claims

1. A linear voltage amplifier circuit comprising:

a DC voltage supply conductor;

a final amplifier stage having a high impedance-output;

an oscillator for producing signal pulses;

a charge pump circuit means connected to said DC voltage supply conductor for being energized therefrom, having an input connected to said oscillator, and having an output with a substantial source impedance,

for producing, at said charge-pump-means output under open circuit conditions, voltage pulses at the frequency of said oscillator signal pulses, said voltage pulses having peak values substantially greater than the voltage applied to said DC voltage supply conductor, said high impedance-output of said final amplifier stage being connected to said charge-pump-means output, said substantial source impedance of said output of said charge pump circuit means serving as a load to said final-amplifier-stage transistor and the high voltage pulses of said charge-pump means serving as a high voltage energizing source to said amplifier transistor.

2. The amplifier of claim 1 wherein said oscillator is a free-running type oscillator for operating at a fixed frequency.

3. The amplifier of claim 1 wherein said charge-pump means consists of diodes, capacitors, and switches for being actuated by said oscillator signal pulses.

4. The amplifier of claim 1 wherein said charge-pump means is a standard voltage multiplier circuit without the output capacitor.

5. The amplifier of claim 1 wherein said substantial source impedance of said charge-pump-means output is large enough that the voltage drop across it due to current flowing through said charge-pump-means output reduces the peak voltage at the charge-pump-means output by more than 50 percent so that the charge-pump means operates approximately as a pulse-current source.

6. An integrated driver circuit of the kind formed in a silicon chip that includes (a) a driver transistor having a control terminal and two output terminals;

(b) a supply voltage pad to which one of said driver-transistor output terminals is connected;

(c) a driver-circuit output pad to which the other of said driver-transistor output terminals is connected and to which an external driver load may be connected; and

(d) a linear amplifier means having one input connected to said driver circuit output pad and including one high-impedance output connected to said driver-transistor input terminal, for regulating the voltage at said driver-circuit output pad, wherein the improvement comprises;

one charge pump circuit means connected to said supply voltage pad for receiving excitation therefrom and having a high-impedance output connected to said one output of said amplifier means for providing an energizing voltage and load impedance to said one output of said amplifier means, said linear amplifier means being additionally for sinking the output current from said one charge pump means, said energizing voltage of said one charge pump means being a series of voltage pulses having a peak amplitude that is substantially greater than a DC supply voltage that may be externally applied to said supply voltage pad.

7. The integrated driver circuit of claim 6 wherein said driver transistor is a field effect transistor.

8. The integrated driver circuit of claim 6 wherein said linear amplifier means includes a differential-amplifier stage with two inputs, one of said two inputs corresponding to said one input connected to said driver circuit output pad, so that the load current in said driver transistor will be regulated with respect to a voltage that may be applied to the other of said two inputs of said differential amplifier stage.

9. The integrated driver circuit of claim 8 wherein said differential-amplifier stage includes a pair of differentially connected field effect transistors, the gates of said pair of transistors corresponding to said two inputs, respectively;

said driver circuit additionally comprising a standard current source connected between said voltage supply pad and the sources of said differentially connected field effect transistors.

10. The integrated driver circuit of claim 8 wherein said one output of said linear amplifier-means has a source-impedance which is commensurate with the source impedance of said one charge-pump-means output, said linear amplifier means including another output having a low-impedance, and said driver circuit additionally comprising a second charge pump means connected to said supply voltage pad for receiving excitation therefrom and having an output connected to said another output of said linear amplifier means for providing energizing voltage pulses and a high-impedance load to said another output of said amplifier means.

11. The integrated driver circuit of claim 10 wherein said differential-amplifier stage is the first linear-amplifier stage, said two differentially connected field effect transistors having their sources connected to the circuit point corresponding to said another low-impedance output of said linear amplifier means.

12. The integrated driver circuit of claim 10 additionally comprising an oscillator having an output connected to said one and to a second charge pump means for synchronously clocking said charge pump means.

13. The integrated driver circuit of claim 10 additionally comprising a synchronizing transistor means through which said output of said second charge pump means is connected to said another output of said linear amplifier means;

said synchronizing transistor having means being further connected to said output of said one pulsing charge pump means for effecting connection between said second charge pump means and said linear amplifier means only during periods when there exists one of said pulses in said one charge pump means.