- Radio RF Electronics
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Decoupling the power supply for high frequency RF and critical circuits
If you want to build RF high frequency or critical circuits, such as extremely high gain
audio amplifiers, you want to decouple the power supply of each individual amplifier/oscillator
to decrease noise and/or feedback (unwanted oscillation).
Critical audio preamplifiers, especially those with high gains, are usually decoupled with
RC low pass filters shown below:
* Decoupling the power supply: Don't forget to decouple the supply with resistors and capacitors:
Solution 1
+ -----+------------------------ common power rail
| ___
+-|___|--+----------+--- + to amplifier stage
R1 | |
__|__ __|__
_____ C1 _____ C2
| |
| |
_|_ _|_
GND GND
Solution 2
___ ___
+ -----|___|--+--------------------------|___|--+-----------
R1 | R2 |
+--------+--- + to amp.stage +--------+- + to amp. stage
| | | |
__|__ __|__ __|__ __|__
_____ C1 _____ C2 _____ C3 _____ C4
| | | |
| | | |
_|_ _|_ _|_ _|_
GND GND GND GND
The resistors are usually in the range of 47Ohm to 2k2; capacitors (C1;C3) from 1μF to 100μF; C2,C3 from 1nF to 100nF
Typical values would be: 100Ω and 4μ7 with 100n
or for single transistor stages (solution 1): 2k2 and 47μ with 100n
You can also use multiple low pass filters for extremely critial applications.
Solution 3
+ -----+------------------------ common power rail
| ___ ___
+-|___|--+----------+------|___|--+----------+----- + to amplifier stage
R1 | | R2 | |
__|__ __|__ __|__ __|__
_____ C1 _____ C2 _____ C3 _____ C4
| | | |
| | | |
_|_ _|_ _|_ _|_
GND GND GND GND
Of course you need to include R1 and R2 to the calculation for the transistor stage.
Last-Modified: Tue, 01 Mar 2005 08:15:21 GMT
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