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ADA4817 spice model

Question asked by Jon@S on Sep 15, 2014
Latest reply on Sep 17, 2014 by Jon@S

Hello everyone,

 

For a projekt we want to use the ADA4817 as a charge sensitive preamplifier. That for we need a low feedback capacitance. The datasheet doesn't say about an internal capacitance between output and inverting input, just about external FB capacitance. For simulation we use LTspice.

 

We found in the circuitfile that there is a capacitance of 800fF between output and inverting input. Because that is nowhere else to find i want to ask if there realy is a capacitance that high between those pins, or if we just can change this in the circuit file if it is less than 800fF.

 

Thank you,

Jonas

 

part of the model follows:

 

* Node assignments

*                            non-inverting input

*                            | inverting input

*                            | | positive supply

*                            | | |  negative supply

*                            | | |  |  output

*                            | | |  |  |

.SUBCKT ADA4817    1 2 99 50 45

 

* FET INPUT STAGE

*Eos 9 2 poly(1) 100 98 4.2m 1

Vos 9 2 1.5m

Cd 1 2 0.1p

Ccm1 1 0 1.3p

Ccm2 2 0 1.3p

J1 5 1 4 pmod

J2 6 9 4 pmod

Ib1 1 0 2p

Ib2 9 0 2p

Dnil 9 42 DX

Vnil 99 42 3.4

Dpil 1 44 DX

Vpil 99 44 3.4

*R3 50 5 1

*R4 50 6 1

HR3 50 55 VR3 1

VR3 55 5 DC 0

HR4 50 66 VR4 1

VR4 66 6 DC 0

I11 99 4 1m

Ccap 45 2 0.8p

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