High cut-off frequency in CE amplifier

Oct 25, 2009 3 Replies
H

I have a CE amplifier.



With real instrumentation, real circuit I got a high cut-off frequency of about 600 kHz while if I repeat it in PSpice I got about 200 MHz (!)



Same circuit with LT Spice I got about 3,5MHz



The device is 2N3904



I saw in an example provided by LTspice that there is a



100pF capacitor between C and B...

Pheraps Miller effect isn't calculated by Spice?



Thanks in advance.


Vote
Twitter Facebook LinkedIn
J

Without a schematic we know nothing. And... What is your definition of cut-off frequency? ...Jim Thompson

| James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | With Half My Brain Tied Behind My Back Still More Clever Than Mr.Prissy Pants
Vote
Twitter Facebook LinkedIn
J

Maybe. How this for a start.

  1. Wrong board lay out. (Un calculated Capacitance &/ induction)
1A. Un expected LC taking place.
  1. Wrong type of resistors.
  2. Not putting a local bypass caps in.
  3. Local bypass caps if #3 has been done, aren't using a non inductive type.
  4. Design has to high of R values, but Spice should of picked up on that.
  5. Your transistor is a fake knock off or just something that was around and stamped as so.

  1. The simulator is just wrong! (no surprise there)

Vote
Twitter Facebook LinkedIn
H

Jamie ha scritto:

This one. Found the issue. Thanks again.

Vote
Twitter Facebook LinkedIn

Join the Discussion

Have something to add? Share your thoughts — no account required.

Didn't find your answer?

Ask the community — no account required