Feedback amplifier circuit

• US 3,922,585 A
• Filed: 01/17/1974
• Issued: 11/25/1975
• Est. Priority Date: 07/24/1969
• Status: Expired due to Term

• Current Assignee: Roland E. Andrews
• Original Assignee: Roland E. Andrews
• Inventors: Andrews, Roland E.
• Primary Examiner(s): Wilbur, Maynard R.
• Assistant Examiner(s): Potenza, J. M.
• Application Number:
  US05/433,993
• Time in Patent Office: 677 Days
• Field of Search: 315/387,388,389,390,403,404,405,396
• US Class Current: 315/389
• CPC Class Codes: H03F 1/302 in bipolar transistor amplifiers H03F1/303, H03F1/305, H03F1/307 take precedence
• CPC Class Codes: H03F 1/34 Negative-feedback-circuit arrangements with or without positive feedback H03F1/02 - H03F1/30, H03F1/38 - H03F1/50, H03F3/50 take precedence ; for rejection of common mode signals H03F3/45479
• CPC Class Codes: H03F 3/26 Push-pull amplifiers; Phase-splitters therefor duplicated single-ended push-pull arrangements or phase-splitters therefor H03F3/30
• CPC Class Codes: H03F 3/3066 the collectors of complementary power transistors being connected to the output
• CPC Class Codes: H03F 3/3081 Duplicated single-ended push-pull arrangements, i.e. bridge circuits using FET's H03F3/3061
• CPC Class Codes: H03K 6/02 Amplifying pulses

Abstract

A feedback amplifier circuit includes a pair of push-pull amplifiers adapted for driving the deflection plates of a cathode ray tube, with each amplifier being provided with a negative feedback circuit including an active amplifying device. As a result of the employment of an amplifying device in each feedback circuit, the conductive loading of output stages is reduced, and therefore the standing current which must be supplied to the amplifier circuit is also reduced.

Claims

1. A feedback amplifier circuit including at least a first amplifying means having an input and an output and exhibiting an open loop gain at said output as compared with said input, said first amplifying means comprising a first common emitter transistor stage driving a second common base transistor stage with the latter providing said output of said first amplifying means and of said amplifier circuit, and negative feedback means coupling said output to said input of said first amplifying means over a range of frequencies at which said first amplifying means operates, said feedback means including a second amplifying means having an input and an output, wherein the input of the second amplifying means is coupled to receive the output of the first amplifying means and impedance means coupling the output of said second amplifying means to the input of the first amplifying means, said second amplifying means comprising an emitterfollower transistor stage coupled from the output of said first amplifying means to said impedance means.

2. The amplifier circuit according to claim 1 wherein said emitter-follower stage is coupled to said common base transistor stage by means of a voltage divider connected at one end thereof to the output of the first amplifying means and provided with a tap thereon connected to the base terminal of said emitter-follower stage.

3. The circuit according to claim 1 further including a current source for said first amplifying means, said current source comprising a fourth transistor having its emitter coupled to a source of voltage and its collector coupled to the collector terminal of said common base transistor stage.

4. The circuit according to claim 3 further including a capacitor coupling the emitter of said common emitter transistor stage to the emitter of said fourth transistor for also driving said fourth transistor.

5. The circuit according to claim 4 adapted to drive a deflection plate of a cathode ray tube and further including a substantially similar circuit driving an opposite deflection plate of the cathode ray tube, said substantially similar circuit differing in the polarity of input signal provided thereto and in the conductivity type of said common-emitter stage.

6. The circuit according to claim 4 further including an additional common base transistor stage interposed in coupling relation between the collector of said common emitter transistor stage and the emitter of said first mentioned common base transistor stage, said circuit further including an a.c. coupling capacitor between the collector of said common emitter transistor stage and the emitter of said first mentioned common base transistor stage.

7. The circuit according to claim 1 wherein said first amplifying means is biased to a low current state and is adapted to receive inputs of a given relative polarity for causing said first amplifying means to draw increased current.

8. A feedback amplifier circuit for driving first and second deflection plates of a cathode ray tube, said circuit comprising:

a first feedback amplifier for driving a first deflection plate of said cathode ray tube, said first amplifier receiving a current input ramp and providing in response thereto a voltage output ramp at said first deflection plate, said first amplifier having a feedback circuit including active amplifying means for coupling a negative feedback signal from the output to the input of said first amplifier, a second feedback amplifier receiving the current ramp input and providing a voltage ramp output for driving said second deflection plate in substantially push-pull relation with the first deflection plate, said second amplifier having a feedback circuit including an active amplifying means coupling a negative feedback signal from the output to the input of said second amplifier, and means intercoupling said first and second amplifiers for transient exchange of currents therebetween.

9. The circuit according to claim 8 wherein first stages of said first and second feedback amplifiers are provided with a common current return.

10. The circuit according to claim 8 wherein said active amplifying means in the feedback circuits of said first and second amplifiers are provided with a common current supply.

11. The circuit according to claim 8 wherein each of said amplifiers comprises a common emitter transistor stage driving a common base transistor output stage, and wherein said active amplifying means in the feedback circuit comprises an emitter follower transistor stage.

12. The circuit according to claim 8 wherein the first stage in each amplifier is in each case biased to a low current state and is adapted to receive one of a pair of push-pull inputs for causing the amplifier to draw increased current.

13. A feedback amplifier circuit comprising:

first transistor means having an input and an output, second plural transistor means having an input and an output and including common collector means therebetween, said output of said first transistor means being connected to said input of said second transistor means defining emitter means thereof, negative feedback means connected from said output of said second transistor means to said input of said first transistor means, and impedance means included in said negative feedback means.