As the final stage of the ECG, I want to build a voltage shifter to shift
the signal into the 0 to 5V range (my analog circuit operates in the -3.6 t=
o
+3.6V range). Looking at the circuit at the bottom of the page here:
http://tinyurl.com/4tyjaho I have a few questions.

1. Is the first opamp (acting as a buffered output) really necessary? What
is its function? Why can't we just take the output from the voltage divider
directly?

2. Is the LM324 buffered? I can't find the answer to this anywhere.

3. The two input resistors are 1M ohms. This is a very high impedance. Why
have they chosen this value?

4. The the gain setting resistors on the second opamp are 220K each,
designed to give the opamp a gain of 2. Do they really need to be 220K each=
?
Or can I just use something like 1K each instead? What difference does it
make, as long as the ratio is the same?
--=20
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