Hello everyone! I'm currently working on something and am finding myself a little stuck. I am trying to determine how to use a photodiode to brighten leds in low light conditions and dim in bright light conditions. I was able to do this with a simple pnp transistor, however, i need to be able to complete this task with an op amp. I was able to construct a current to high voltage converter, and also a high gain current amplifier but was at a lack of knowledge as to how to use it to dim or brighten lights. So does anyone know of a circuit that does what i am attempting to do, or does someone know how to use a current or voltage to dim a led running of a simple battery and resistor. Each time i connect my op amps output to my led, it either makes the battery draw more or less current, without affecting the lights. The values do not matter, given a circuit i can interpret and scale to my needs, i just need to see it done.