The U237B series are driving circuits for a 5 or 10-LED bar display having an integrated current generator whose current is adjusted to 20mA.
Light-emitting diodes are connected in series to reduce power dissipation and to have the same current flow to the supply in every operating condition.
For red LED the supply voltage is 12 volts whereas in the case of green or yellow diodes, the voltage is 16 volts.
