Post History
I was looking for electret condenser microphone preamp topologies. I’d like the preamp to run on a single supply, so I’ll have to introduce an output offset. Saw two topologies for introducing th...
#5: Post edited
by
misk94555
·
2025-01-12T18:01:11Z (5 days ago)
additional information
I was looking for electret condenser microphone preamp topologies. I’d like the preamp to run on a single supply, so I’ll have to introduce an output offset. Saw two topologies for introducing an output offset. How do they compare in practice?- The 1st topology adds the bias to the input signal, and connects the op-amps feedback setting resistor to ground through a capacitor.
- 
- [ST application note AN1534](https://www.st.com/resource/en/application_note/cd00004352-ts971-based-electret-condenser-microphone-amplifier-stmicroelectronics.pdf) uses this topology (fig. 1) .
- [This Analog Dialoue](https://www.analog.com/en/resources/analog-dialogue/articles/avoiding-op-amp-instability-problems.html) article uses it too.
- The 2nd topology connects the op-amp’s resistor network to a virtual ground.
- 
Don't know if it's important for this question, but maybe I should mention it. I’m planning the preamp with a differential output. The negative signal of the differential pair will be created with an inverting op-amp, which isn’t shown in the schematics above. The output of the non-inverting op-amp will be the positive signal of the differential pair.
- I was looking for electret condenser microphone preamp topologies. I’d like the preamp to run on a single supply, so I’ll have to introduce an output offset. Saw two topologies for introducing the output offset. How do they compare in practice?
- The 1st topology adds the bias to the input signal, and connects the op-amps feedback setting resistor to ground through a capacitor.
- 
- [ST application note AN1534](https://www.st.com/resource/en/application_note/cd00004352-ts971-based-electret-condenser-microphone-amplifier-stmicroelectronics.pdf) uses this topology (fig. 1) .
- [This Analog Dialoue](https://www.analog.com/en/resources/analog-dialogue/articles/avoiding-op-amp-instability-problems.html) article uses it too.
- The 2nd topology connects the op-amp’s resistor network to a virtual ground.
- 
- Don't know if it's important for this question, but maybe I should mention it. I’m planning the preamp with a differential output. The negative signal of the differential pair will be created with an inverting op-amp, which isn’t shown in the schematics above. [I can add it to the schematics, if anyone wants to see it.] The output of the non-inverting op-amp will be the positive signal of the differential pair.
- **edit [I should have mentioned it from the start]:**
- The proposed op-amp is [TL972](https://www.ti.com/product/TL972) ([PDF datasheet](https://www.ti.com/lit/ds/symlink/tl972.pdf)). 9.5 MHz gain × bandwidth. 4.7 nV/sqrt(Hz) .
- The audio band of interest is between 20 Hz to 4 kHz (great horned owl, plus generous margin). I don’t mind designing the preamp for the full 20 Hz to 20 kHz audio rage, though.
#4: Post edited
by
Nick Alexeev
·
2025-01-12T16:05:59Z (5 days ago)
Single-supply non-inverting op-amp with output offset. How to create an output offset?
- Single-supply non-inverting op-amp with an output offset. How to create the output offset?
#3: Post edited
by
misk94555
·
2025-01-12T04:01:17Z (6 days ago)
added another reference link
#2: Post edited
by
misk94555
·
2025-01-12T04:00:34Z (6 days ago)
- I was looking for electret condenser microphone preamp topologies. I’d like the preamp to run on a single supply, so I’ll have to introduce an output offset. Saw two topologies for introducing an output offset. How do they compare in practice?
- The 1st topology adds the bias to the input signal, and connects the op-amps feedback setting resistor to ground through a capacitor.
- 
[ST application note AN1534](https://www.st.com/resource/en/application_note/cd00004352-ts971-based-electret-condenser-microphone-amplifier-stmicroelectronics.pdf) uses this topology (fig. 1) .- The 2nd topology connects the op-amp’s resistor network to a virtual ground.
- 
- Don't know if it's important for this question, but maybe I should mention it. I’m planning the preamp with a differential output. The negative signal of the differential pair will be created with an inverting op-amp, which isn’t shown in the schematics above. The output of the non-inverting op-amp will be the positive signal of the differential pair.
- I was looking for electret condenser microphone preamp topologies. I’d like the preamp to run on a single supply, so I’ll have to introduce an output offset. Saw two topologies for introducing an output offset. How do they compare in practice?
- The 1st topology adds the bias to the input signal, and connects the op-amps feedback setting resistor to ground through a capacitor.
- 
- [ST application note AN1534](https://www.st.com/resource/en/application_note/cd00004352-ts971-based-electret-condenser-microphone-amplifier-stmicroelectronics.pdf) uses this topology (fig. 1) .
- [This Analog Dialoue](https://www.analog.com/en/resources/analog-dialogue/articles/avoiding-op-amp-instability-problems.html) article uses it too.
- The 2nd topology connects the op-amp’s resistor network to a virtual ground.
- 
- Don't know if it's important for this question, but maybe I should mention it. I’m planning the preamp with a differential output. The negative signal of the differential pair will be created with an inverting op-amp, which isn’t shown in the schematics above. The output of the non-inverting op-amp will be the positive signal of the differential pair.
#1: Initial revision
by
misk94555
·
2025-01-12T03:57:49Z (6 days ago)
Single-supply non-inverting op-amp with output offset. How to create an output offset?
I was looking for electret condenser microphone preamp topologies. I’d like the preamp to run on a single supply, so I’ll have to introduce an output offset. Saw two topologies for introducing an output offset. How do they compare in practice? The 1st topology adds the bias to the input signal, and connects the op-amps feedback setting resistor to ground through a capacitor.  [ST application note AN1534](https://www.st.com/resource/en/application_note/cd00004352-ts971-based-electret-condenser-microphone-amplifier-stmicroelectronics.pdf) uses this topology (fig. 1) . The 2nd topology connects the op-amp’s resistor network to a virtual ground.  Don't know if it's important for this question, but maybe I should mention it. I’m planning the preamp with a differential output. The negative signal of the differential pair will be created with an inverting op-amp, which isn’t shown in the schematics above. The output of the non-inverting op-amp will be the positive signal of the differential pair.