Op Amp Amplifier with -25 to 55 dB Attenuation-Gain range
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- Опубліковано 24 сер 2024
- How to design an electronic amplifier with wide range of attenuation and gain using one operational amplifier and one potentiometer? what range of attenuation and gain we can realize for the single op amp electronic amplifier? What Gain-Bandwidth product (GBW) should we consider for the needed OpAmp for analog audio signal processing vs for video/multimedia applications? What Op Amp choices are available from integrated circuit designers like Texas Instruments or Analog Devices? These questions are discussed in this variable attenuation-gain amplifier with wide gain dynamic range. The presented circuit analysis for the analog circuit example in this video shows as much as -25 dB (attenuation) and as high as 55dB gain can be realized by this design. A combination of op amp virtual short and gain of non-inverting amplifier are used to find the minimum and maximum gain of the presented analog amplifier.
Thanks for watching. For more examples please see:
Op Amp Amplifier with Electronic Gain Control: How does it work? ua-cam.com/video/NoNgQpbj77Y/v-deo.html
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For more analog circuits and signal processing examples see the Analog Circuits Video playlist: ua-cam.com/play/PLrwXF7N522y4c7c-8KBjrwd7IyaZfWxyt.html
I hope these Circuit design and analysis videos are interesting and useful. 🙋♂
A greatness of this schematic is that you can use a linear potentiometer and get a log scale attenuation. A very demanded feature for an audio amp
Thanks for highlighting the log scale attenuation using single linear Potentiometer and single op amp. To your good point, Another example of adjustable Attenuator circuit for audio signal processing applications is the VCA voltage-controlled Attenuator discussed in ua-cam.com/video/cFzYZsPEtP0/v-deo.html
You don't get a log scale attenuation, just a wide range. The logs are in the dB calculation, not the circuit. Nobody said anything about the distribution of the gain with pot position or the noise gain. Similar circuits are use for audio trimming by connecting the pot wiper to the inverting input which gives symmetrical gain/attenuation with 0dB in the centre and only noise gain with signal gain.
@@hintoninstruments2369 Thanks for watching and sharing your thoughts. As you noted, this circuit is presented as an interesting minimal design example to achieve a very wide gain/attenuation range using just one op amp, one Potentiometer & few resistors. The Gain has a nonlinear relationship with the wiper position.
These are very valuable videos here on youtube.
Thank you for encouraging comment. Glad that my videos are useful. Btw, given that there are nearly 200 videos in my Analog & electronic circuits playlist, is it easy to search for specific topic among those 200 videos?
Thank you for video. Seems like input impedance will vary with the gain.
You are welcome. Thanks for sharing your thoughts. While you are right that input impedance changes as we adjust the Potentiometer, the input impedance has the minimum of R1 (4.7kOhm in this example) and the maximum of R1+10 kOhm (14.7 kOhm ) meaning the change is not substantial (not orders of magnitude). If need be, We can also further decrease dynamic range of input impedance by increasing the value of R1. An alternative method is discussed in Another technique is discussed in Op Amp Amplifier with high input impedance and large voltage gain ua-cam.com/video/jriZt1OR5Ok/v-deo.html . I hope this is helpful.
For more examples please see my Analog & Op Amp Circuit Videos playlist ua-cam.com/play/PLrwXF7N522y4c7c-8KBjrwd7IyaZfWxyt.html
Input impedance variation is inevitable. May be you can cascade a Commom-collector stage on 'Vin' to have almost constant input impedance.
@@Parirash123 thanks for sharing your thoughts and your design suggestion. Another technique is discussed in Op Amp Amplifier with high input impedance and large voltage gain ua-cam.com/video/jriZt1OR5Ok/v-deo.html
Ultimately, if constant and very large input impedance is required in a given design, Maybe just adding a buffer stage op amp at input is the safest way to satisfy such absolute requirement. This is illustrated in the video of Instrumentation Amplifier with Electronic Gain Control ua-cam.com/video/C4tghZ-q6Zs/v-deo.html . I hope this is helpful.
hi really appreciate your videos helped me learn a lot . i'm in a predicament designing a similar circuit .
my specification : Input +-10Vac or +-5Vac or 3.3Vac / 50Mhz . Output:+-.5Vac / 50Mhz , which equals to , respectively to 1/20 gain = 0.05 = -26.02dB for +-10Vac and 1/10 gain = .1 = -20dB for +-5Vac and 1/6.6 gain = .1515 = -16.39 for +-3.3Vac input signal . i really prefer to achieve this with FDA configuration but single-ended I/O op amp would suffice . i have many issues finding a circuit capable of this requirements . 1- your design for achieving -25dB inputs 1/101 of the input signal into op-amp . 2- i cannot find a find an op-amp with a reliable spice model to simulate this setup before designing and every simulation attempt is failed so far 3- output noise on the opamps is very reliant on the Rf value , extracting this value from datasheet and employing it in simulation software produces a very different output than expected ..
4- i'm having a hard time finding suitable op amp for this task
i would really appreciate if you could help me to find solution for these problems , btw i'm designing this as an ADC Driver and also i'm using proteus for simulation .
You're welcome Sam. Glad that my channel is useful. Regarding the choice of Op Amp, as discussed in minute 18:00 in this video, I suggest CMOS low-noise op amps from Texas Instruments of Analog Devices with zero or near zero offsets and very low drift. I also suggest a decent slew rate which of course depends on the maximum input frequency in your applications. Also see the Texas Instruments Op Amp used in ua-cam.com/video/HYqKQ-nUf5o/v-deo.html video. Alternatively, you might consider TI FET-input TLV9301 Op Amp or more expensive TI LMH6714 for higher frequency (say video applications). I hope this is helpful.
@@STEMprof thanks for your help .