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AD795 spice model question

Question asked by fbartra on Nov 5, 2015
Latest reply on Nov 5, 2015 by fbartra

I am trying to verify the open loop gain for this op amp using the spice model provided on your website

 

for some reason I can not get the same gain below 1kHZ

below is my simulation file (very simple)

 

any comments will be appreciated

 

Fausto Bartra

 

* this simulation to check the AD795 fq response

 

*-------------------------

*         Power supplies

*-------------------------

*

VP15    P15        0        +15

VN15    N15        0        -15

Vin        pp        0        AC 1

*----------------------------------

*        Amplifier

*----------------------------------

* differential amplifier

Rl        Vo        0        100k

Rn        np        0        100

Rp        pp        0        100

 

XU1A     pp        np        P15        N15        Vo         AD795

 

.save     pp np  Vo

 

*----------------------------------

*        Simulation

*----------------------------------

 

*PLOT TRAN -1 1 A=+2.5V

 

*.OPTION KeepLastSetup=False

*Selected Circuit Analyses:

.OP

 

*.TRAN <Tstep> <Tstop> [Tstart [dTmax]] [modifiers]

*.TRAN 1u 20m 0 1u

 

*.ac <oct, dec, lin> <Nsteps> <StartFreq> <EndFreq>

.AC Dec 1000 1 10Meg

 

* AD795 SPICE Macro-model

* Description: Amplifier

* Generic Desc: 8/30V, JFET, OP, Low Pwr, Low Noise, 1X

* Developed by: JOM / ADSC

* Revision History: 08/10/2012 - Updated to new header style

* 1.0 (11/1994)

* Copyright 1990, 2012 by Analog Devices.

*

* Refer to http://www.analog.com/Analog_Root/static/techSupport/designTools/spiceModels/license/spice_general.html for License Statement. Use of this model

* indicates your acceptance with the terms and provisions in the License Statement.

*

* BEGIN Notes:

*

* Not Modeled:

*

* Parameters modeled include:

*

* END Notes

*

* Node assignments

*                non-inverting input

*                | inverting input

*                | | positive supply

*                | | |  negative supply

*                | | |  |  output

*                | | |  |  |

.SUBCKT AD795    1 2 99 50 30

*

* INPUT STAGE & POLE AT 40 MHZ

*

R3   5  50    .719

R4   6  50    .719

CIN  1   2    2E-12

C2   5   6    1.383E-9

I1   99  4    100E-3

IOS  1   2    0.1E-12

EOS  65  1    POLY(1)  17 24  50E-6  1

J1   5   2    4   JX

J2   6   7    4   JX

EN   7  65    43  0  1

GN1  0   1    47  0  1E-6

GN2  0   2    61  0  1E-6

GB1  2  50    POLY(3) 4,2 5,2 50,2 0 1E-12 1E-12 1E-12

GB2  7  50    POLY(3) 4,7 6,7 50,7 0 1E-12 1E-12 1E-12

*

EREF 98  0    24  0   1

*

* VOLTAGE NOISE GENERATOR

*

VN1  41  0    DC 2

RS1  41 42    8E3

RS2  42 43    1.2E9

CS1  42 43    398E-11

RS3  43 44    1.2E9

CS2  43 44    398E-11

RS4  44 45    8E3

VN2  0  45    DC 2

*

* CURRENT NOISE GENERATOR

*

VN3  46  0    DC 2

RN5  46 47    41.5

RN6  47 48    41.5

VN4  0  48    DC 2

*

* CURRENT NOISE GENERATOR

*

VN5  60  0    DC 2

RN7  60 61    41.5

RN8  61 62    41.5

VN6  0  62    DC 2

*

* SECOND STAGE & POLE AT 2.213 HZ

*

R5   9  98    719203

C3   9  98    1.00E-7

G1   98  9    5  6  1.39

V2   99  8    3.025

V3   10 50    3.025

D1   9   8    DX

D2   10  9    DX

*

* NEGATIVE ZERO AT 15 MHZ

*

R6   11 12     1E6

R7   12 98     1

E2   11 98     9  24  1E6

VX1  84  0

EX1  83  0     11 12  1

FX1  11 12     VX1  -1

CX1  83 84     10.6E-15

*

* POLE AT 20 MHZ

*

R8   13 98     1E3

C5   13 98     7.96E-12

G2   98 13     12 24  1E-3

*

* POLE AT 20 MHZ

*

R9   14 98     1E3

C6   14 98     7.96E-12

G3   98 14     13 24  1E-3

*

* POLE AT 20 MHZ

*

R10  15 98     1E3

C7   15 98     7.96E-12

G4   98 15     14 24  1E-3

*

* COMMON-MODE GAIN NETWORK WITH ZERO AT 300 HZ

*

R11  16 17     1E6

C8   16 17     5.3E-10

R12  17 98     1

E3   16 98     POLY(2) 1  98  2  98  0  1.585  1.585

*

* POLE AT 20 MHZ

*

R13  18 98     1E3

C9   18 98     7.96E-12

G5   98 18     15 24  1E-3

*

* OUTPUT STAGE

*

R14  24 99     2000E3

R15  24 50     2000E3

FSY  99 50     POLY(2) V7 V8 -98.7E-3 1 1

R16  29 99     360

R17  29 50     360

L1   29 30     1E-8

G8   29 99     99 18  2.78E-3

G9   50 29     18 50  2.78E-3

V4   25 29     2.0

V5   29 26     2.0

D3   18 25     DX

D4   26 18     DX

F1   29  0     V4  1

F2   0  29     V5  1

G6   98 70     29 18 2.78E-3

D5   70 71     DX

D6   72 70     DX

V7   71 98     DC 0

V8   98 72     DC 0

*

* MODELS USED

*

.MODEL JX PJF(BETA=9.67  VTO=-2.000  IS=0.50E-12 RD=0.1

+ RS=0.1 CGD=1E-15 CGS=1E-15)

.MODEL DX   D(IS=1E-15 RS=10 CJO=1E-15)

.ENDS AD795

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