How to simulate the noise of differential amplifier

[lordfire]

.ac differential amp hspice

as below is the spice sentence

X1 IN1 IN2 OUT1 OUT2 AMP1
vin1 in1 0 dc 0.75V ac=1 , 0
vin2 in2 0 dc 0.75V ac=1 , 180

.ac dec 10 1K 10g
.noise v(out1,out2) v(in1,in2) 10


but noise simulation failed, log shows
**warning**: invalid input noise source .. analysis omitted


how to simulate the noise of diff AMP. accurately

 

[flushrat]

amplifier noise analysis testbench in spice

try this netlist, your .noise statement is wrong

X1 IN1 IN2 OUT1 OUT2 AMP1
vin in 0 dc=0 ac=1
vcom com 0 0.75
ein1 in1 com in 0 0.5
ein2 in2 com in 0 -0.5
eout out 0 out1 out2 1

.ac dec 10 1K 10g
.noise v(out) vin 10

 

[lordfire]

simulating the noise of a differential amplifier

Thanks, flushrat

it's helpful

 

[winsonpku]

differential amplifier+netlist

i think the vin ac should be 2
if ac=1,then vdb(out1)=vdb(out2)but not the same as vdb(out)
vdb(out) maybe 3db larger then the other two

try this netlist, your .noise statement is wrong

X1 IN1 IN2 OUT1 OUT2 AMP1
vin in 0 dc=0 ac=1
vcom com 0 0.75
ein1 in1 com in 0 0.5
ein2 in2 com in 0 -0.5
eout out 0 out1 out2 1

.ac dec 10 1K 10g
.noise v(out) vin 10

 

[flushrat]

differential amplifier noise analysis

vdb(out) is differential gain, whereas vdb(out1) is single-end gain
so vdb(out) must be 3dB larger than vdb(out1)

i think the vin ac should be 2
if ac=1,then vdb(out1)=vdb(out2)but not the same as vdb(out)
vdb(out) maybe 3db larger then the other two

try this netlist, your .noise statement is wrong

X1 IN1 IN2 OUT1 OUT2 AMP1
vin in 0 dc=0 ac=1
vcom com 0 0.75
ein1 in1 com in 0 0.5
ein2 in2 com in 0 -0.5
eout out 0 out1 out2 1

.ac dec 10 1K 10g
.noise v(out) vin 10

 

[Ashtaroth]

what is the ein ?

why did you add it, is it neccessary for the noise analysis?????

 

[nafaiz]

try this netlist, your .noise statement is wrong

X1 IN1 IN2 OUT1 OUT2 AMP1
vin in 0 dc=0 ac=1
vcom com 0 0.75
ein1 in1 com in 0 0.5
ein2 in2 com in 0 -0.5
eout out 0 out1 out2 1

.ac dec 10 1K 10g
.noise v(out) vin 10

dear flushrat,

i'm new in analog ic design. can u tell me are there books or manuals that tell what is ein, in1, com etc. when and where to write them in ur netlist. i tried to find books about ic design but only found few books with few examples on how to write netlist in hspice. if u do have a soft copy about that book or manual can u pls upload it here.

regards

 

[flushrat]

ein is the differential input . Using e elements is better than using two vsources in simulation (refer to "A test bench for differential circuits" on www.designers-guide.com )

It is not necessary for noise analysis.

what is the ein ?

why did you add it, is it neccessary for the noise analysis?????

Added after 2 minutes:

refer to hspice manual

try this netlist, your .noise statement is wrong

X1 IN1 IN2 OUT1 OUT2 AMP1
vin in 0 dc=0 ac=1
vcom com 0 0.75
ein1 in1 com in 0 0.5
ein2 in2 com in 0 -0.5
eout out 0 out1 out2 1

.ac dec 10 1K 10g
.noise v(out) vin 10

dear flushrat,

i'm new in analog ic design. can u tell me are there books or manuals that tell what is ein, in1, com etc. when and where to write them in ur netlist. i tried to find books about ic design but only found few books with few examples on how to write netlist in hspice. if u do have a soft copy about that book or manual can u pls upload it here.

regards