Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

7402 Pinout Difference

Status
Not open for further replies.

jack0987

Member
Looking up images for the pinout of the 7402, two versions came up.
Is this common?
Which is correct?

7402-AltPinout.png
7402-Pinout.jpg
 
Both images are correct.

The image on the left is for a CMOS CD4001. This is NOT directly equivalent to a bipolar SN7402 in the right image, either electrically (voltages and currents) or physically (pinout). Note that the left image power pin is Vdd (the correct designation for a CMOS part) as opposed to the right image of a Bipolar TTL part with a power pin labeled Vcc. This is because a bipolar transistor has a collector (c) while a CMOS transistor has a drain (d).

cc stands for common collector, a type of amplifier circuit. When FET logic came about, they changed the last letter to d for drain. Rather than use the technically correct Vcd (Voltage, common-drain), they went with dd for consistency and error reduction

ak
 
Thanks for the response.

I am using the TTL one (an MC74HC02) on the right.

Is it good practice to to ground all unsed inputs?
 
Last edited:
Thanks for the response.

I am using the TTL one (an MC74HC02) on the right.

Is it good practice to to ground all unsed inputs?

Probably, a lot depends on the circuit configuration in the chips (might be better both high, might already be pulled high or low internally?), and if you're wanting minimum power consumption - it's more of an issue in CMOS, where inputs can drift and put the gate in an analogue state, greatly increasing consumption.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top