In this circuit, a PNP transistor sources current. The base voltage is about 0.7 V less than the emitter voltage. So with 10.3 V on the base, the emitter has about 11 V and R1 sees about 1 V ...

Author Mazi Hosseini describes a simple, low-cost, voltage-controlled current source using two op amps that provides a good range of current and maximum load.

Each circuit component has two branch gains, one for each direction of signal transmission. If the destination node is an ideal voltage source with zero impedance, then the gain is zero and not shown ...

There are two voltage sources in a bandgap reference. One is the base-emitter drop of a forward biased bipolar transistor. It has an inherent –2-mV/°C temperature coefficient that's balanced by ...