Op-amp input capacitance

G

George

Guest
Hello,

Is there any way to estimate the input capacitance of an op-amp (say the
TL082) in unity gain, voltage follower mode? A friend estimates it as
about 12 pF based on some transient voltage lab tests. I couldn't find
any info about this on the TI data sheets, unless I missed it.

Also, does the Pspice op-amp model for the TL082 include input
capacitance? My guess is that is does not.

George
 
On Tue, 06 Dec 2005 09:44:57 -0600, George <steber@execpc.com> wrote:

Hello,

Is there any way to estimate the input capacitance of an op-amp (say the
TL082) in unity gain, voltage follower mode? A friend estimates it as
about 12 pF based on some transient voltage lab tests. I couldn't find
any info about this on the TI data sheets, unless I missed it.

Also, does the Pspice op-amp model for the TL082 include input
capacitance? My guess is that is does not.

George
Click to expand...
If it's a DIP, it's about 4pF per pin... almost all of it package
related, NOT on the chip itself... chip pad is probably ~100fF.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
Jim Thompson wrote:
On Tue, 06 Dec 2005 09:44:57 -0600, George <steber@execpc.com> wrote:

Hello,

Is there any way to estimate the input capacitance of an op-amp (say the
TL082) in unity gain, voltage follower mode? A friend estimates it as
about 12 pF based on some transient voltage lab tests. I couldn't find
any info about this on the TI data sheets, unless I missed it.

Also, does the Pspice op-amp model for the TL082 include input
capacitance? My guess is that is does not.

George

If it's a DIP, it's about 4pF per pin... almost all of it package
related, NOT on the chip itself... chip pad is probably ~100fF.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
Click to expand...
It's a DIP. The 4 pF sounds reasonable. Thanks for the info.

George
 
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