I need a simple(=3D cheap) relatively stable(temp and noise) dc amplifier t= hat can take a voltage from 0 to 5V and output from around 0V(not critical)= to near Vcc(but arbitrary) somewhat linearly.
I'm thinking a simple bjt amplifier with temp compensation will work decent= ly but the issue is linearity and range.
e.g., the output voltage of an ideal CE amplifier is Vout =3D Vcc - Rc/Re*V= in
Of course when Vin =3D 0 volts, Vout =3D Vcc. When Vin is 5V we get Vout = =3D Vcc - 5Rc/Re but we would like 0V or some low fixed voltage instead.=20
Adding temperature compensation makes things worse since it effects our upp= er range(which is more crucial than the lower range) since Vin cannot swing= down to 0V(I'm assuming the simple diode compensation scheme generally use= d).
In any case the requirements are
- Relatively cheap and easy to built(e.g., a few discrete components)/
- Amplifies a voltage from [0, Vin_max] to approximately [0, Vcc] with the= upper range being more important. Vcc is somewhat arbitrary =3D=3D> May ch= ange after the design of the circuit =3D=3D> no component values can depend= on Vcc to achieve specs. (Obviously one can assume that Vcc is within all = the maximum voltage ratings of the components)
- Temperature stable/compensated. The temperature range will vary only aro= und 10-20C.
- Relatively low noise(not that big of an issue since caps can take care o= f the big problems).
Vin ranges from 0 to 5V and Vcc ranges from about 50V to 500V.