Purpose of capacitors, and diodes being wired to ground?

[strosectro]

I've seen it in schematics, but never understood the reason of wiring capacitors, resistors, and/or diodes to ground, ie coming from the emitter of a transistor. What's the point?

 

[tresca]

It depends what the transistors being used for. I'm guessing that because you are seeing resistors and/or capacitors wired from the emitter to ground from a transistor, the transistor is being used as an amplifier.

When used as an amplifier, there are 2 types of voltages that make it work. DC and AC.
With DC, you bias the transistor to work in a certain region. You then take certain values from your DC calculations to make the AC amplification work well.

The reason those resistors are there is to help bias the transistor for amplification and to provide stability, since transistors are temperature dependent. By adding resistor, Re, you help stabalize it with temperature changes.

What happens to a capacitor in a DC circuit ? It acts as an open circuit right ? But what happens when you connect it in an AC circuit ? It acts as a short.

In order to seperate AC and DC signals, capacitors are used. This way, you dc voltages dont affect your AC stuff, and your AC stuff doesnt affect your DC stuff.

 

[Wond3rboy]

It depends what the transistors being used for. I'm guessing that because you are seeing resistors and/or capacitors wired from the emitter to ground from a transistor, the transistor is being used as an amplifier.

When used as an amplifier, there are 2 types of voltages that make it work. DC and AC.
With DC, you bias the transistor to work in a certain region. You then take certain values from your DC calculations to make the AC amplification work well.

The reason those resistors are there is to help bias the transistor for amplification and to provide stability, since transistors are temperature dependent. By adding resistor, Re, you help stabalize it with temperature changes.

What happens to a capacitor in a DC circuit ? It acts as an open circuit right ? But what happens when you connect it in an AC circuit ? It acts as a short.
In order to seperate AC and DC signals, capacitors are used. This way, you dc voltages dont affect your AC stuff, and your AC stuff doesnt affect your DC stuff.

Nicely put but about the short it should be rephrased as ' A capacitor responds to a finite AC frequency as a finite impedance'.

 

[strosectro]

It depends what the transistors being used for. I'm guessing that because you are seeing resistors and/or capacitors wired from the emitter to ground from a transistor, the transistor is being used as an amplifier.

When used as an amplifier, there are 2 types of voltages that make it work. DC and AC.
With DC, you bias the transistor to work in a certain region. You then take certain values from your DC calculations to make the AC amplification work well.

The reason those resistors are there is to help bias the transistor for amplification and to provide stability, since transistors are temperature dependent. By adding resistor, Re, you help stabalize it with temperature changes.

What happens to a capacitor in a DC circuit ? It acts as an open circuit right ? But what happens when you connect it in an AC circuit ? It acts as a short.

In order to seperate AC and DC signals, capacitors are used. This way, you dc voltages dont affect your AC stuff, and your AC stuff doesnt affect your DC stuff.

Thanks for the response. How would a person know which value to pick? Calculation?