Describe the basic SHA operation with the help of its four mode specifications.
Sample-and-hold amplifier (SHA) is a unity gain amplifier with a mode control switch where the input of the amplifier is connected to a time-varying signal. A trigger pulse at the mode control switch causes it to read the input at the instance of the trigger and maintain that value until the next trigger pulse. Usually the signal is electrical, but other forms, such as optical and mechanical forms, are possible. Also denoted S/H.