Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

size of transistor for driving another transistor

Status
Not open for further replies.

padoh

Junior Member level 2
Joined
Jul 2, 2012
Messages
21
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,458
can a 1mm transistor be driven by a 20um transistor for length 130nm? is there any way of determining this?
 

erikl

Super Moderator
Staff member
Joined
Sep 9, 2008
Messages
8,114
Helped
2,694
Reputation
5,368
Reaction score
2,294
Trophy points
1,393
Location
Germany
Activity points
44,061
can a 1mm transistor be driven by a 20um transistor for length 130nm? is there any way of determining this?

Sure: from the equation / Q=CV=It / you can get the slew rate at the large transistor's gate δV/δt = I/C .
I is the drive transistor's max. driving current capability, C is the gate input capacitance Cgg of the driven transistor.

This is quite a good approximation.
 

dick_freebird

Advanced Member level 5
Joined
Mar 4, 2008
Messages
7,572
Helped
2,188
Reputation
4,382
Reaction score
2,082
Trophy points
1,393
Location
USA
Activity points
60,506
This is a 50:1 taper which is abnormal. Best prop delay in
a logic chain is around 3:1, I've done clock trees at 2:1
when pressing against the process speed capability, and
stick to roughly 4:1 for power FET driver taper chains
(or 4:1 "off", 8:1 "on" if I'm doing a "ballistic" anti-shoot-
through design). Never have I been happy with so weak
a gate drive, in a switching circuit.

Though I suppose if you wanted a controlled slew, this
is one way to get it. Not as well controlled, though, as
a stiff driver and a series resistor, in respect to process
and temperature and supply variation.
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top