View ba683a datasheet:

Audio ICs LED level meter driver, 12-point, power scale, dot or bar display BA683A The BA683A is a monolithic IC for LED power meter applications. The display level range is 9mVrms to 380mVrms (Typ.) divided into 12 points with interval spacings of 3dB. The constant current outputs can be set using an external resistor. FApplications Level meters for all types of audio equipment applica- tions FFeatures 1) 12-point power meter driver for bar/dot displays. 4) Built-in half-wave rectifier amplifier. 2) Fixed-current outputs that can directly drive LEDs. 5) With bar-type display, by connecting four LEDs in se- 3) Output current can be set using external resistors al- ries, power dissipation is reduced. lowing different types of LEDs to be used in combina- tion. FBlock diagram