Identify the usage of the passive components below
Jan 23, 2018 7:48:03 GMT
Post by lingyueqing on Jan 23, 2018 7:48:03 GMT
As part of furthering my understanding of opamps and audio electronics, I put this headphone amplifier together on a breadboard. Only one channel shown:
The circuit works like a charm, and is based on a number of schematics I scrounged on the web (swapping alternative parts in and out with whatever I had in my junk drawer).
I'd like some help to identify the purpose of some of the passive components, how their values are chosen and why they're necessary. The parts I understand (although correct me if I'm wrong!):
The 10uF (C2) and 22nF (C3) capacitors are the IC power decoupling (bypass) capacitors. The 10uF provides a small measure of voltage smoothing in case of voltage dips, while the 22nF filters out high frequency noise.
The 4Kohm and 1Kohm (R1 & R2) resistors form the negative feedback network, and set the gain of the amplifier - in this case, 5 [(4/1)+1].
The 22Kohm (R6) resistor on the audio input is a pull-down resistor, there to give an open circuit a path to ground if no audio source is connected (noise filtering).
Questions:
Typically, I've found recommended values of 10uF and 10nF for decoupling capacitors. I used 22nF capacitors for C3 because that was all I had, but it seems to work fine. How are these values determined, and what is ideal?
There is a ferrite bead on the input of each power rail (green on the schematic). I used 45ohm ferrites (again, all I had) although the source schematic called for "6.9ohm" ferrites. I understand that ferrite beads are used to block EMI interference... somehow... but again how these values selected?
What does C1 (150pF) parallel to the audio input do (and how was its value chosen)?
Ditto for R3 (1Kohm) on the audio input?
Ditto for R4 and R5 (10ohm) on the output of each opamp?
Lastly, the buffer (BUF634 datasheet:www.ti.com/lit/ds/symlink/buf634.pdf) itself. I understand that the first opamp (OPA2227 datasheet: www.kynix.com/uploadfiles/pdf65976/OPA2227P.pdf) is amplifying the voltage, which I found both on kynix semiconductors: www.kynix.com/, and that the buffer essentially does the same for current. Does this mean that if the load wants to draw more current, the buffer provides more current than the OPA2227 alone could supply?
Thanks in advance.
The circuit works like a charm, and is based on a number of schematics I scrounged on the web (swapping alternative parts in and out with whatever I had in my junk drawer).
I'd like some help to identify the purpose of some of the passive components, how their values are chosen and why they're necessary. The parts I understand (although correct me if I'm wrong!):
The 10uF (C2) and 22nF (C3) capacitors are the IC power decoupling (bypass) capacitors. The 10uF provides a small measure of voltage smoothing in case of voltage dips, while the 22nF filters out high frequency noise.
The 4Kohm and 1Kohm (R1 & R2) resistors form the negative feedback network, and set the gain of the amplifier - in this case, 5 [(4/1)+1].
The 22Kohm (R6) resistor on the audio input is a pull-down resistor, there to give an open circuit a path to ground if no audio source is connected (noise filtering).
Questions:
Typically, I've found recommended values of 10uF and 10nF for decoupling capacitors. I used 22nF capacitors for C3 because that was all I had, but it seems to work fine. How are these values determined, and what is ideal?
There is a ferrite bead on the input of each power rail (green on the schematic). I used 45ohm ferrites (again, all I had) although the source schematic called for "6.9ohm" ferrites. I understand that ferrite beads are used to block EMI interference... somehow... but again how these values selected?
What does C1 (150pF) parallel to the audio input do (and how was its value chosen)?
Ditto for R3 (1Kohm) on the audio input?
Ditto for R4 and R5 (10ohm) on the output of each opamp?
Lastly, the buffer (BUF634 datasheet:www.ti.com/lit/ds/symlink/buf634.pdf) itself. I understand that the first opamp (OPA2227 datasheet: www.kynix.com/uploadfiles/pdf65976/OPA2227P.pdf) is amplifying the voltage, which I found both on kynix semiconductors: www.kynix.com/, and that the buffer essentially does the same for current. Does this mean that if the load wants to draw more current, the buffer provides more current than the OPA2227 alone could supply?
Thanks in advance.