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| honest... |
 Posted: Sun Oct 25, 2009 4:07 am |
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Guest
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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. |
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| Jim Thompson... |
| Posted: Sun Oct 25, 2009 8:50 am |
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Guest
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On Sun, 25 Oct 2009 11:07:57 +0100, honest <none at (no spam) host.com> wrote:
[quote]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.
[/quote]
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 |
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| Jamie... |
| Posted: Sun Oct 25, 2009 9:09 am |
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Guest
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honest wrote:
[quote]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.
Maybe.[/quote]
How this for a start.
1. Wrong board lay out. (Un calculated Capacitance &/ induction)
1A. Un expected LC taking place.
2. Wrong type of resistors.
3. Not putting a local bypass caps in.
4. Local bypass caps if #3 has been done, aren't using a non inductive
type.
5. Design has to high of R values, but Spice should of picked up on that.
6. Your transistor is a fake knock off or just something that was
around and stamped as so.
7. The simulator is just wrong! (no surprise there) |
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| honest... |
| Posted: Fri Oct 30, 2009 8:12 am |
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Guest
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Jamie ha scritto:
[quote]1. Wrong board lay out. (Un calculated Capacitance &/ induction)
[/quote]
This one. Found the issue.
Thanks again. |
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