The opamp needs to be able to feed the lamp, so you need a high-output one. Then bild it, check frequency against the value of C, change C accordingly. The lamp makes sure of a stable output without distortion.
But which of the C do I change? The one connected to ground? Which of the R is part of the RC circuit? (The circuit is a bit confusing because it uses 2 identical R & C values.)
If I want to make the RC variable, which R do I replace with a pot (or fixed
Also, this op amp (LF155) is specified as dual-supply type. I need a single supply op amp. Will the R-C connection to ground of this circuit be connected to -Vcc regardless if it is a single or dual supply op amp?
You change them both, both circuits have to balance at the wanted frequency. Changing only one will degrade oscillator quality. If you can lay your hands on a tuning cap, they often contain two sections, and make testing rather easy.
I need some advice regarding the grounding of the parallel R & C.
The LF155 is a dual-supply amp. I need a single-supply amp.
I presume that in this circuit the ground is chosen because it is the mid-point between the dual supplies (ie, +/-15). With a single-supply amp, this point is not mid-point but rather it is the "negative supply" point.
How should this circuit change for use with a single-supply amp?
Among conventional op-amps, there isn't much that really makes a single-supply op-amp special. Often the only thing about an op-amp that inspires the manufacturer to call it a single-supply op-amp is the fact that the common mode range (the input) includes the negative supply. At least that's my take on it. More to the point is that your APPLICATION appears to require a dual supply. Almost any old op-amp will do, like the one Phil named or even a good old
741. You need a central reference point for that circuit, as indicated by the ground symbol. It's actually not hard to take a single supply and effectively split it in two. You need a voltage divider and a voltage follower. The voltage divider is two resistors in series connected across your power supply that creates a voltage reference at the midpoint between Vcc+ and Vcc-. But it has high impedance, which means that drawing current from it will drag the voltage up and down, something you don't want. So you put a buffer in there, a voltage follower. If you get a dual op-amp you can use the spare op-amp as the voltage follower. To use an op-amp as a voltage follower you connect the non-inverting input to the voltage divider, and connect the inverting input to the op-amp's output. The op-amp's output is then a low-impedance source at the midpoint of your power supply. It's like taking a 12 volt battery and magically turning it into two 6 volt batteries in series. You can also use a bjt as a voltage follower.