Welcome to EMH!
EMH is the Electronics Math Helper. It currently does only a few calculations, but
more will be added as time allows.
Special thanks to Peter Snowberg for assisting with this project.
Voltage Divider
Calculates the output of a voltage divider.
Parallel Resistors
Calculates resistors in parallel.
Linear Potentiometer
This provides a way to fake a custom linear pot with a one of a larger
value. Values are in kiloOhms, so a 1M pot would be entered as 1000.
The resulting value can fluctuate as the knob is turned. This may
be a problem in certain DC applications.
Tapered Potentiometer
This provides a way to fake a custom tapered pot with a linear one of a larger
value. Values are in kiloOhms, so a 1M pot would be entered as 1000.
The resulting value can fluctuate as the knob is turned. This may
be a problem in certain DC applications.
Transistor Bias
This lets you plug in the bias values and see the effects. Resistor values
are in kiloOhms! This is useful for finding bias values that are more tolerant
to Hfe, resistor, or voltage variances.
Warning: Germanium calculations are probably not accurate, although it should get close. Some
tweaking will be required.
FuzzFace
Warning: This program is accurate for designing allsilicon FuzzFace clones. Germanium transistor
calculations are available, but may not be accurate. Use this circuit at
Geofex to get more accurate readings for germanium
transistors, but beware that other factors can effect the outcome.
Update 5/26/05: Program now works mathematically instead of doing iterations to find
appropriate values. Germanium/hybrid calculations should be more accurate now.
This calculator lets you plug in some values, and it will pick the right R1 to bias the circuit correctly.
Use whatever resistor is closest to the computed value of R1. This allows you to quickly test parameters such as
the gain control value and feedback bias resistor value R4.
After calculating, breadboard the circuit. Test to ensure the collector of Q2 is near 4.5v, especially when
germaniums are involved. Adjust R1 slightly until it's right.
You need to know the Beta values for your transistors. Datasheet values won't do,
so measure the values with a DMM that provides the function, or use the Geofex circuit to obtain the value. Q1's
beta value needs to be especially accurate, as even a 20% difference can throw things off.
Trimpot Cheater
Calculates four series resistors to be used instead of a trimpot. (The unused resistors are
simply shorted across.) Sixteen levels of precision are available:
Code 1 2 3 4
 
0    
1    X
2   X 
3   X X
4  X  
5  X  X
6  X X 
7  X X X
8 X   
9 X   X
10 X  X 
11 X  X X
12 X X  
13 X X  X
14 X X X 
15 X X X X
