High-Frequency VGA Has Digital Control TM High-Frequency VGA Has Digital Control Application Note April 1998 AN9641.1 Introduction R2, R3, and the -5V supply form a bias circuit that sets VB3 to -4.4V when there is no DAC output current (the voltage You can use variable-gain ampliers (VGAs) in many types across R1 is zero), which occurs at a digital input of all ones. of system……