Driving a 4-Digit 7-Segment LED display with only 3 pins, using two 74HC595 shift registers and some n-channel FETs

This circuit is a variation of the DoubleShift experiment that demonstrated how to use two 74HC595 shift registers and some NPN BJTs to drive a 4-digit 7-segment display with only 3 Arduino GPIO pins.

The only difference here is that the S9013 NPN BJTs are replaced with 2N7000 n-channel FETs.

When fully on (e.g. displaying 8888), it appears the display and associated components on the breadboard are drawing an average of about 2.47mA (compared to 2.87mA with BJTs).

• 74HC595 Datasheet
• 2N7000 Datasheet
• KW4-561 Datasheet - not matching the part I have, but a pretty stanrd example
• a good How to.. question at EE.SE
• 2 Shift Registers 74HC595 Cascading with LED Display