CA1116704A - Precision rectifier circuit - Google Patents
Precision rectifier circuitInfo
- Publication number
- CA1116704A CA1116704A CA000314779A CA314779A CA1116704A CA 1116704 A CA1116704 A CA 1116704A CA 000314779 A CA000314779 A CA 000314779A CA 314779 A CA314779 A CA 314779A CA 1116704 A CA1116704 A CA 1116704A
- Authority
- CA
- Canada
- Prior art keywords
- transistor
- output
- amplifier
- base
- input
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/22—Arrangements for measuring currents or voltages or for indicating presence or sign thereof using conversion of ac into dc
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Rectifiers (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A precision rectifier circuit using an operational amplifier connected in a differential amplifier mode. At least one of the rectifying feedback connections is provided by the emitter-base path of a transistor and a half-wave rectified version of the input signal is obtained from the collector of the transistor. A biassing circuit is disclosed for use when both rectifying feedback connections are transistors to reduce the output voltage swing between one transistor turning off and the other turning on.
A precision rectifier circuit using an operational amplifier connected in a differential amplifier mode. At least one of the rectifying feedback connections is provided by the emitter-base path of a transistor and a half-wave rectified version of the input signal is obtained from the collector of the transistor. A biassing circuit is disclosed for use when both rectifying feedback connections are transistors to reduce the output voltage swing between one transistor turning off and the other turning on.
Description
i7~
Background of the Invention . .
This invention relates to a precision rectifier circuit. Such clrcuits are used when signal waveforms are to be measured with precision and distortion of the ~aveform must be avoided.
It is known that when diodes are used for rectifi-cation a significant signal loss occurs due to the forward bias necessary before the diode conducts. Circuits using the rectifying diodes in the feedback path of an operational amplifier reduce this loss by a factor approximately equal to the gain of the amplifier. Such circuits are shown in Canadian patent No. 954,938, issued September 17, 1974 in the names of Dammann et al. and U.S. patent No. 3,553,566, issued January 5, 1971 in the name of Nagy.
The present invention replaces at least one of the rectifying diodes by the emitter-base path of a transistor.
By taking the output signal from the collector of the transistor a high output impedance source is provided suitable Eor feeding a grounded current meter or a recorder. The invention also includes a biassing circuit for use when both rectifying diodes are replaced by transistors to reduce the output voltage swing between one transistor turning off and the other turning on.
Specifically, the invention relates to a ?recision recti-fier comprising an amplifier having an input and an output, a signal input terminal connected to the amplifier input, a diode connected between the ampli~ier output and lnput, and a transistor with its base~emitter path connected between 29 to the amplifier output and input providing a feedback path jvb/
: , l6~4 poled in the opposite sense to that through the diode.
In its restricted aspect, the invention relates to a precision rectifier comprising a differential amplifier having an inverting input, a non-inverting input and an output. A
signal input terminal is connected to the non-inverting input.
First and second transistors of opposite polarity have their base-emitter paths provide a feedback connection between the amplifier output and the inverting input. A biassing network is connected between the amplifier output and the base of the i 10 second transistor to promote the turn on of the second transistor when the voltage at the amplifier output passes through zero.
The biassing network comprises a pair of diodes arranged in series with the base of the second transistor and is oppositely poled thereto. A resistive voltage divider applies biassing voltages to the junction of the diodes and to the base of the second transistor.
Brief Description of the Drawings __ Figure 1 is a schematic diagram of a precision rectifier circu:it in accordance with the present invention; and Pigure 2 is a schematic diagram of a modification of the circuit of Figure l.
Description of the Preferred Embodiments ... . ~
Referring now to Figure 1, a differential amplifier 10 has its non-inverting input connected to a suitable source of biassing potential at terminal 19. Terminals ll and 12 are provided to receive tlle signal input with terminal 12 being 27 grounded and terminal 11 connected to the inverting input of
Background of the Invention . .
This invention relates to a precision rectifier circuit. Such clrcuits are used when signal waveforms are to be measured with precision and distortion of the ~aveform must be avoided.
It is known that when diodes are used for rectifi-cation a significant signal loss occurs due to the forward bias necessary before the diode conducts. Circuits using the rectifying diodes in the feedback path of an operational amplifier reduce this loss by a factor approximately equal to the gain of the amplifier. Such circuits are shown in Canadian patent No. 954,938, issued September 17, 1974 in the names of Dammann et al. and U.S. patent No. 3,553,566, issued January 5, 1971 in the name of Nagy.
The present invention replaces at least one of the rectifying diodes by the emitter-base path of a transistor.
By taking the output signal from the collector of the transistor a high output impedance source is provided suitable Eor feeding a grounded current meter or a recorder. The invention also includes a biassing circuit for use when both rectifying diodes are replaced by transistors to reduce the output voltage swing between one transistor turning off and the other turning on.
Specifically, the invention relates to a ?recision recti-fier comprising an amplifier having an input and an output, a signal input terminal connected to the amplifier input, a diode connected between the ampli~ier output and lnput, and a transistor with its base~emitter path connected between 29 to the amplifier output and input providing a feedback path jvb/
: , l6~4 poled in the opposite sense to that through the diode.
In its restricted aspect, the invention relates to a precision rectifier comprising a differential amplifier having an inverting input, a non-inverting input and an output. A
signal input terminal is connected to the non-inverting input.
First and second transistors of opposite polarity have their base-emitter paths provide a feedback connection between the amplifier output and the inverting input. A biassing network is connected between the amplifier output and the base of the i 10 second transistor to promote the turn on of the second transistor when the voltage at the amplifier output passes through zero.
The biassing network comprises a pair of diodes arranged in series with the base of the second transistor and is oppositely poled thereto. A resistive voltage divider applies biassing voltages to the junction of the diodes and to the base of the second transistor.
Brief Description of the Drawings __ Figure 1 is a schematic diagram of a precision rectifier circu:it in accordance with the present invention; and Pigure 2 is a schematic diagram of a modification of the circuit of Figure l.
Description of the Preferred Embodiments ... . ~
Referring now to Figure 1, a differential amplifier 10 has its non-inverting input connected to a suitable source of biassing potential at terminal 19. Terminals ll and 12 are provided to receive tlle signal input with terminal 12 being 27 grounded and terminal 11 connected to the inverting input of
- 2 -jvb/
7~L
differential amplifier 10 vla a resistor 13. Appropriate voltage bias is supplied to the ampli-Eier via terminal 14.
The amplifier output is fed back to the input side of resistor 13 via a diode 15. Another feedback connection oE
opposite polarity is provided by the base-emitter path of a transistor 16. The precision rectifier output is obtained from the collector of transistor 16 via a terminal 17. IE a high impedance, current output circuit is required resistor 18 can be omitted. Conversely, if a voltage output is required the collector current from transistor 16 is passed to ground through resistor 18.
In operation, terminal 19 is suppl:ied with a positîve voltage, typically 0.7 times the voltage applied to terminal l~i. Normal operational amplifier feedback causes the current in resistor 13 to equal the current flowing in either d:iode 15 or the emitter of transistor ]6. On positive going input signals the amplifier output wi]l swing negatively causing transistor 16 to conduct. Since transistor 16 is selected to have a high current gain almost all the emitter current also flows in the collector circuit producing a half-wave rectified version of the input signal. Transistor 16 may be a Darlington pair which, as is known, is the equivalent of a single transistor of high current gain.
Figure 2 illustrates modifications to the circuit o-E
Figure 1. The same reference numerals are used for elements already described in connection with Figure 1. As before, transistor 16 provides a feedback path from the output of 28 amplifier 10 to its inverting input. In distinction to the jvb/
ii7~'~
c:ircuit of Figure 1, however, the signal input from terminal 11 is applied to the non-inverting input via a biassing network formed by capacitor 21 and resistors 22 and 23.
This provides a high impedance input.
The feedback connection provided by diode 15 in Figure 1 is replaced by the base-emitter path of a further transistor 25 in Figure 2. If required, a further output of the precision rectifier is available from the collector of transistor 25 at terminal 27. Resistor 28 can be provided if a voltage output is required. The performance of the rectifier circuit is improved by including a biassing network consisting of diodes 31, 32 and resistors 33, 3~l.
When a source of positive bias is applied to terminal 35 the network functions to maintain the base of transistor 25 positive with respect to the output of amplifier 10. Thus, as the output signal from amplifier 10 changes from negative to positive the amplitude of the voltage swing between transistor 16 turning off and transistor 25 turning on is greatly reduced. The time required between turn off and turn on is correspondingly reduced enabling the circuit to operate at higher frequencies for a given precision.
jvb/
7~L
differential amplifier 10 vla a resistor 13. Appropriate voltage bias is supplied to the ampli-Eier via terminal 14.
The amplifier output is fed back to the input side of resistor 13 via a diode 15. Another feedback connection oE
opposite polarity is provided by the base-emitter path of a transistor 16. The precision rectifier output is obtained from the collector of transistor 16 via a terminal 17. IE a high impedance, current output circuit is required resistor 18 can be omitted. Conversely, if a voltage output is required the collector current from transistor 16 is passed to ground through resistor 18.
In operation, terminal 19 is suppl:ied with a positîve voltage, typically 0.7 times the voltage applied to terminal l~i. Normal operational amplifier feedback causes the current in resistor 13 to equal the current flowing in either d:iode 15 or the emitter of transistor ]6. On positive going input signals the amplifier output wi]l swing negatively causing transistor 16 to conduct. Since transistor 16 is selected to have a high current gain almost all the emitter current also flows in the collector circuit producing a half-wave rectified version of the input signal. Transistor 16 may be a Darlington pair which, as is known, is the equivalent of a single transistor of high current gain.
Figure 2 illustrates modifications to the circuit o-E
Figure 1. The same reference numerals are used for elements already described in connection with Figure 1. As before, transistor 16 provides a feedback path from the output of 28 amplifier 10 to its inverting input. In distinction to the jvb/
ii7~'~
c:ircuit of Figure 1, however, the signal input from terminal 11 is applied to the non-inverting input via a biassing network formed by capacitor 21 and resistors 22 and 23.
This provides a high impedance input.
The feedback connection provided by diode 15 in Figure 1 is replaced by the base-emitter path of a further transistor 25 in Figure 2. If required, a further output of the precision rectifier is available from the collector of transistor 25 at terminal 27. Resistor 28 can be provided if a voltage output is required. The performance of the rectifier circuit is improved by including a biassing network consisting of diodes 31, 32 and resistors 33, 3~l.
When a source of positive bias is applied to terminal 35 the network functions to maintain the base of transistor 25 positive with respect to the output of amplifier 10. Thus, as the output signal from amplifier 10 changes from negative to positive the amplitude of the voltage swing between transistor 16 turning off and transistor 25 turning on is greatly reduced. The time required between turn off and turn on is correspondingly reduced enabling the circuit to operate at higher frequencies for a given precision.
jvb/
Claims (6)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A precision rectifier comprising:
an amplifier having an input and an output, a signal input terminal connected to the amplifier input, a diode connected between the amplifier output and input, and a transistor with its base-emitter path connected between the amplifier output and input providing a feedback path poled in the opposite sense to that through the diode.
an amplifier having an input and an output, a signal input terminal connected to the amplifier input, a diode connected between the amplifier output and input, and a transistor with its base-emitter path connected between the amplifier output and input providing a feedback path poled in the opposite sense to that through the diode.
2. A precision rectifier as set out in claim 1 wherein the output signal is the collector current of the transistor and is a half-wave rectified version of the signal applied to the signal input terminal.
3. A precision rectifier as set out in claim 1 wherein said diode is constituted by the base-emitter path of a second transistor.
4. A precision rectifier as set out in claim 3 further including a biassing network connected between the amplifier output and the base of said second transistor to promote the turn on of said transistor when the output voltage passes through zero.
5. A precision rectifier as set out in claim 1 wherein said amplifier is a differential amplifier, the signal input terminal is connected to the non-inverting input and the signal fed back from the output is connected to the inverting input.
6. A precision rectifier comprising a differential amplifier having an inverting input, a non-inverting input and an output, a signal input terminal connected to the non-inverting input, first and second transistors of opposite polarity having their base-emitter paths providing a feedback connection between the amplifier output and the inverting input, a biassing network connected between the amplifier output and the base of the second transistor to promote the turn on of the second transistor when the voltage at the amplifier output passes through zero, said biassing network comprising a pair of diodes arranged in series with the base of said second transistor and oppositely poled thereto and a resistive voltage divider applying biassing voltages to the junction of the diodes and to the base of the second transistor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000314779A CA1116704A (en) | 1978-10-30 | 1978-10-30 | Precision rectifier circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000314779A CA1116704A (en) | 1978-10-30 | 1978-10-30 | Precision rectifier circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1116704A true CA1116704A (en) | 1982-01-19 |
Family
ID=4112748
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000314779A Expired CA1116704A (en) | 1978-10-30 | 1978-10-30 | Precision rectifier circuit |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1116704A (en) |
-
1978
- 1978-10-30 CA CA000314779A patent/CA1116704A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |