US3825849A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Small signal amplifier
Assignee: Motorola Solutions Inc
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Filing: 1972-07-12
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Granted: 1974-07-23
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Expires: 1992-07-12
Abstract
Abstract A transistor amplifier stage followed by an emitter follower stage with the emitter follower providing an output and feedback to the base of the amplifier stage and an opposite conductivity type transistor connected between the base and common. A microphone or other small signal generating device providing an AC or DC signal is connected between the base and common of the transistor so that the transistor operates as a variable conductivity diode with the conductivity varying in accordance with the small signal input. Thus the microphone is direct coupled to the amplifier and the small signal varies about the common or ground potential with the feedback maintaining the entire circuit at a desired operating point.
Inventors
- 👤 D Linder
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 11:22
CPC Classifications
H; H03; H03F; H03F3/00; H03F3/181; H03F3/183
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
221 words
An improved small signal amplifier comprising: a. amplifying means including a first conductivity type semiconductor device having first, second and control electrodes and output means, said first electrode being direct current coupled to a reference potential; b. a second conductivity type semiconductor device direct current coupled between the control electrode of said first conductivity type semiconductor device and said reference potential; c. constant current means connecting said output means to said second conductivity type semiconductor device and the control electrode of said first conductivity type semiconductor device for supplying a substantially constant current thereto in a quiescent state; and d. direct current means coupled between said second conductivity type device and said reference potential for receiving a small signal varying about said reference potential and varying the current flowing through said second conductivity type semiconductor device and the conductivity thereof in response thereto, said coupled means and said second conductivity type semiconductor device being connected between the first and control electrodes of said first conductivity type semiconductor device for providing an alternate current path in parallel with the first and control electrodes of said first conductivity type semiconductor device to vary the amount of current being applied to the control electrode of said first conductivity type semiconductor device in response to the small signal applied to said second conductivity type device.
Claim 2
Dependent Claim
221 words
An improved small signal amplifier comprising: a. amplifying means including a first conductivity type semiconductor device having first, second and control electrodes and output means, said first electrode being direct current coupled to a reference potential; b. a second conductivity type semiconductor device direct current coupled between the control electrode of said first conductivity type semiconductor device and said reference potential; c. constant current means connecting said output means to said second conductivity type semiconductor device and the control electrode of said first conductivity type semiconductor device for supplying a substantially constant current thereto in a quiescent state; and d. direct current means coupled between said second conductivity type device and said reference potential for receiving a small signal varying about said reference potential and varying the current flowing through said second conductivity type semiconductor device and the conductivity thereof in response thereto, said coupled means and said second conductivity type semiconductor device being connected between the first and control electrodes of said first conductivity type semiconductor device for providing an alternate current path in parallel with the first and control electrodes of said first conductivity type semiconductor device to vary the amount of current being applied to the control electrode of said first conductivity type semiconductor device in response to the small signal applied to said second conductivity type device.
Claim 3
Dependent Claim
36 words
An improved small signal amplifier as set forth in claim 1 wherein the output means is a transistor connected in an emitter follower stage having a control electrode coupled to the output of the semiconductor device.
Claim 4
Dependent Claim
53 words
An improved small signal amplifier as set forth in claim 2 wherein the output of the amplifier is obtained from the emitter follower stage and the constant current means connecting the output means to the second conductivity type device includes a feedback resistor which applies the output to said second conductivity type device.
Claim 5
Dependent Claim
54 words
An improved small signal amplifier as set forth in claim 3 including in addition means biasing the second conductivity type semiconductor device and the first conductivity type semiconductor device for maintaining the output of the amplifier at a value approximately midway between common and supply potentials applied to the amplifier in a quiescent state.
Claim 6
Dependent Claim
31 words
An improved small signal amplifier as set forth in claim 4 wherein the second conductivity type semiconductor device is a PNP type transistor with the collector connected to a common terminal.
Claim 7
Dependent Claim
32 words
An improved small signal amplifier as set forth in claim 5 having in addition a small signal generating device connected directly between the collector and the base of the PNP type transistor.
Claim 8
Dependent Claim
20 words
An improved small signal amplifier as set forth in claim 6 wherein the small signal generating device includes a microphone.
Claim 9
Dependent Claim
222 words
An improved small signal amplifier comprising: a. an amplifier stage includIng a first transistor having a first conductivity type with emitter, collector and control electrodes, said emitter electrode being direct current coupled to a reference potential; b. an emitter follower stage coupled to receive the output of said amplifier stage at an input thereof and providing an output; c. a second transistor having an opposite conductivity type with emitter, collector and control electrodes, said collector electrode being direct current coupled to the reference potential; d. feedback means connecting the output of said emitter follower stage to the control electrode of said first transistor and to the emitter electrode of said second transistor for supplying operating current thereto; and e. small signal input means direct current coupled between the collector electrode and the control electrode of said second transistor for applying a small signal varying about the reference potential to vary the conductivity between the emitter electrode and the control electrode in response to small signal inputs to thereby vary the current flowing through said second transistor, the emitter and collector electrodes of said second transistor being direct current coupled between the control and emitter electrodes of said first transistor for varying the amount of current being applied to the control electrode of the first transistor in response to the small signal input.
Claim 10
Dependent Claim
222 words
An improved small signal amplifier comprising: a. an amplifier stage includIng a first transistor having a first conductivity type with emitter, collector and control electrodes, said emitter electrode being direct current coupled to a reference potential; b. an emitter follower stage coupled to receive the output of said amplifier stage at an input thereof and providing an output; c. a second transistor having an opposite conductivity type with emitter, collector and control electrodes, said collector electrode being direct current coupled to the reference potential; d. feedback means connecting the output of said emitter follower stage to the control electrode of said first transistor and to the emitter electrode of said second transistor for supplying operating current thereto; and e. small signal input means direct current coupled between the collector electrode and the control electrode of said second transistor for applying a small signal varying about the reference potential to vary the conductivity between the emitter electrode and the control electrode in response to small signal inputs to thereby vary the current flowing through said second transistor, the emitter and collector electrodes of said second transistor being direct current coupled between the control and emitter electrodes of said first transistor for varying the amount of current being applied to the control electrode of the first transistor in response to the small signal input.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-07-22 | 1978-01-21 | 1978-07-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-07-22 | 1982-01-21 | 1982-07-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-07-22 | 1986-01-21 | 1986-07-23 | $7700.00 | Window Closed / Lapsed |