The Amplifier Circuit Schematic Given is Lacking the Components' Values

Thread Starter

Alyssa 1

Joined Feb 13, 2019
18
I'm making a project in which the amplifier circuit is based on this open-source project: https://www.hackster.io/metrowest_a...R-AjRhpRLj0mh6LpKVaK0leOluvmfEOFRofYsBueA4HAU .

The only problem is that, from the above schematic, the diode is lacking its value, the capacitors are lacking its corresponding voltages and the resistors are lacking its corresponding power. I only have basic knowledge about electronics and I really want to try make this project for tuning my guitar but I cannot make the circuit without the right components. Thank you.
 

Ya’akov

Joined Jan 27, 2019
9,071
The only problem is that, from the above schematic, the diode is lacking its value, the capacitors are lacking its corresponding voltages and the resistors are lacking its corresponding power. I only have basic knowledge about electronics and I really want to try make this project for tuning my guitar but I cannot make the circuit without the right components. Thank you.
Welcome to AAC!

The reason those values are missing is because they can be derived from other aspects of the circuit. The diodes function tells you what type is needs to be, and like the other components, the voltage and current it must handle tells you the rest.

Since you know the supply voltage, you can work out the required ratings for the capacitors. In isolation, a capacitors voltage is a maximum rating, and so it needs to be somewhat more than the maximum voltage the capacitor will see. There are standard values, so picking one with some margin from among those is sufficient.

The resistor ratings are similar. Since resistors generate heat in operation, the power ratings are actually a measure of heat capacity. Ohm’s Law can tell you how much power a resistor will disparate. Most schematics will call it a special case resistor that is expected to drop a larger voltage and so needs a larger resistor. By using the supply voltage and the resistance, you can calculate the current through the resistor and so the power handling requirements.

The post previous to mine has the answers worked out, but almost certainly simply form experience not calculation. You can do the calculation if needed until you have the experience. You will find a lot of help here on specifics.

Good luck with your project!
 
Last edited:

dl324

Joined Mar 30, 2015
16,846
The only problem is that, from the above schematic, the diode is lacking its value, the capacitors are lacking its corresponding voltages and the resistors are lacking its corresponding power.
Diode - anything convenient. Maximum reverse voltage is going to be 3.3V and most opamps can't source more than 25mA.

Caps - 10V or higher.

Resistors - 1/4W.
 

Thread Starter

Alyssa 1

Joined Feb 13, 2019
18
The reason those values are missing is because they can be derived from other aspects of the circuit.
Wow, thank you so much. This is new knowledge to me. If I'll encounter problems like this one, I know how to solve it already. This knowledge will greatly help me in the future. Thank you so much.
 

dl324

Joined Mar 30, 2015
16,846
Thank you so much. ^^
I did a calculation to see if any resistor would need to be larger than 1/4W.

\( \small P = \frac{V^2}{R} => R = \frac{V^2}{P} = \frac{5V^2}{0.25W} = 100\Omega \)

So any resistor smaller than 200 ohms would need to be larger than 1/4W (assuming a very conservative power derating of 50%).
 

Audioguru

Joined Dec 20, 2007
11,248
Audioguru, the OP Amp is TL972, output rail-to-rail very-low-noise OpAmp. Since I cannot find the ic, I substituted it with MCP6002.
The instructions say that it uses the very low noise TL972 audio opamp, not the general purpose MCP6002 that produces lots of noise. I do not know if the circuit ignores the noise (rumble and hiss). Digikey and many other vendors have thousands of TL972 opamps in stock.
 
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