Bridge Audio Amplifier Explained

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Dual Op Amp Bridge Audio Amplifier is analyzed and explained in this video. How does Bridge Audio Amplifier work? How to compute the gain of audio amplifier? and what are the proper choices of the circuit components? These questions are answered in this 204th video in my analog circuit design playlist on RU-vid. This circuit is designed with two operational amplifiers and a signal DC voltage supply to deliver few hundred watts power to an audio speaker. A quick DC analysis is provided in this video to show how positive and negative DC supplies are provided to both Op Amps using single voltage supply. Then the lower end of frequency response is analyzed and is shown that is defined by the series RC resistor-capacitor in the circuit. The values of the resistor and capacitor are then selected to support audio amplification above 30Hz. Then the amplifier gain is computed using KVL (Kirchhoff Voltage Law) and op amp virtual short and negative feedback. It is shown that the gain of this bridge audio amplifier is 1+2R2/R1.

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9 мар 2024

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@STEMprof 3 месяца назад

Dual Op Amp Bridge Audio Amplifier is analyzed and explained in this video. For more Circuit videos: Electric Guitar Amplifier to XLR Audio Signal ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-X4y8cwZdGEk.html Op Amp Amplifier with Electronic Gain Control ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-NoNgQpbj77Y.html Push-Pull Power Amplifier with Darlington Transistors ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-866MYibo8yE.html VCA Electronic Gain Control (Part 1): Voltage-Controlled Attenuator Overview ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-cFzYZsPEtP0.html Power Amplifier Design (Class A) with Transformer ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-gKlJrqGqeCI.html PhotoDiode Amplifier with Data Compression Explained ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-hqrRx2ufAwg.html Amplifier with -25 to 55 dB Attenuation-Gain range ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-oyz6lTGd2Xo.html Electronic Gain Control for Op Amp Amplifier ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-NoNgQpbj77Y.html Push-Pull Power Amplifier with Darlington Transistors ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-866MYibo8yE.html Thermometer Circuit Design with Op Amp & BJT transistor ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-55YsraFE0rg.html PhotoDiode Amplifier with Op Amp and MOSFET Explained ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-1c3EJ2d4pVI.html Instrumentation Amplifier with Electronic Gain Control ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-C4tghZ-q6Zs.html Voltage Regulator Op Amp Circuit with Foldback current limiting ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-VN4_qF9DvBM.html Push-Pull Power Amplifier Design with Op Amp, Sziklai Darlington Transistors ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-8BFzsi7-Vbs.html And the Analog Circuits Video playlist: ru-vid.com/group/PLrwXF7N522y4c7c-8KBjrwd7IyaZfWxyt I hope these Circuit design and analysis videos are interesting.

@erikev 3 месяца назад

How will the workload be distributed between the amps if the input signal has a slight unintended offset?

@STEMprof 3 месяца назад

That's a good question. In this analysis we are applying an input AC signal in differential mode with zero DC offset. I would suggest using AC decoupling capacitors at input so that we isolate input terminals of the Op Amps from any DC residual of the applied input signal. I hope this is helpful.

@sc0or 3 месяца назад

If we take a really good input opamp and reinforce the output with for instance BUF634 (number of them, I mean 30-60) we'll have an excellent hi-fi amplifier with power enough for a big room. If we provide a really good power supply, that will be considered a hi-end amplifier with no doubts.

@STEMprof 3 месяца назад

Good points especially regarding using combination of Texas Instruments BUF634 High-Speed Buffers or its newer version BUF634A to provide high enough AC current to speaker. Alternatively newer Texas Instruments products like OPA2673 Dual, High Output Current Operational Amplifier might be an interesting choice for this circuit. 👍

@sc0or 3 месяца назад

@@STEMprof Yes, OPA2673 might be interesting for some applications, may be it will be enough for a headphone driver, however I don't see it inside a power amp with its +-6.5V supply range. May be with a floating rail this will be possible.

@STEMprof 3 месяца назад

@sc0or Yes, good point regarding supply range. We can also use high-current power transistors at the output of Op Amp to defer power delivery to transistor so that we can have a wider choice for the type of op amp for this audio amplifier.

@sc0or 3 месяца назад

@@STEMprof Sure, but even mid power bjts mostly are not fast enough. I can remember KSC2690 and 2SC3503 with a bandwidth to 150MHz. High power transistors are not an option at all. And this is why buf634 with a bandwidth to 250MHz is unique (relatively unique due to high current output). I listened to an amplifier built with buf634 which was able to amplify PAL signal -) It sounded as a hi-end device. However it didn't use a bridge architecture and was limited with 20W@8Ohm

@STEMprof 3 месяца назад

@@sc0or Great points regarding the importance of monitoring the max speed that power transistor is able to achieve. But I think there are Power Transistors that can easily handle Audio frequencies with 20 to 40A Collector current. Few examples are OnSemi 25 Ampere 200W 2N6338, 2N6341 High-Power NPN Silicon Transistors www.digikey.com/en/products/detail/onsemi/2N6338G/1475307 and possibly Fairchild FGH20N6S2, FGP20N6S2, FGB20N6S2 600V 125W N-Channel IGBT www.digikey.com/en/products/detail/rochester-electronics-llc/FGP20N6S2/11508896

@karamveersingh7290 3 месяца назад

Beautiful bridge audio amplifier work balance input and tone control ?

@STEMprof 3 месяца назад

Thank you. Glad that you liked this dual op amp audio amplifier video.

@AnalogDude_ Месяц назад

LOL,I fail to understand how this works, but configured s non inverting opamp, so both raise and fall a the same time. I simulated the circuit, i even put a 8 ohm resistor between both opamps as analog for the speaker, the current was like u amps over the 8 ohm resistor. I even rotated one of the opamps like it would seem logical, one pushing and the other pulling, but the behavior was the same. I'm curious how this Bridge mode works, my car amp has this.

@STEMprof Месяц назад

Thanks for your interest in this circuit and sharing your thoughts/observations. As explained starting in minute 8:30 , It is like a differential amplifier for AC input signal that is applied between the non-inverting terminals of the two op amps. As the input AC voltage increases, it pushes up the positive input terminal of say the left op amp higher than the other one's. As a result an AC current flows from left to right through the resistor R1 (C1 impedance is practically zero in the frequency range of interest).

@AnalogDude_ Месяц назад

@@STEMprof Hey, i made a pcb of my class AB amp, now i wanna make a pcb for the power side, bridge rectifier, etc. I wanna add a soft start to prevent inrush current of the capacitors, using mosfets. for the positive rail it's not so hard, but applying the same voltage of the gate of mosfet of the positive rail on the negative's gate doesn't work, since there is like 40 Volt difference. the negative rail moves much faster if you use caps as time delay. I tried various sources, like stack exchange. You happen to know a method of moving 2 mosfets a the same time on 2 voltage extremes?