This circuit was found in 1960s Radio Electronics. The circuit uses components from that time. The triac is according to the controlled load. The sensor is a common LDR.
With this configuration we have a voltage follower, amplifier with unit gain, in which the output...
This circuit is from the Linear Circuits Application of Texas Instruments, using an operational amplifier...
This amplifier, suggested by National Semiconductor (Now Texas Instruments), has high input...