transistor is a semiconductor device used to amplify or switch electronic signals. The transistor is the fundamental building block of computers, other modern electronic devices. Some transistors are packaged individually but most are found in integrated circuits.
Operational amplifier, or op-amp , is a DC-coupled high-gain electronic voltage amplifier with differential inputs and, usually, a single output. Typically the output of op-am is controlled ethr by negative feedback, which largely determines the magnitude of its o/p voltage gain, or by positive feedback, which facilitates regenerative gain and oscillation.