Noise Calculations

Calculating Noise Requirement

• "A calculation of required noise and current swings on the SCUBA-2 MUX wafer leads", Kent Irwin, 2003

TES-bias Noise Performance

See Noise Analysis of LN_Bias lines in Bias Card

Depending on the mce configuration, a single-ended or differential, a unipolar or bipolar circuit is used to drive the TES bias. Here is some non-accurate(!!) calculation of the estimated noise performance of the TES bias circuitry. (python scrip to be posted...)

Assumptions

R_shunt = 3.4 m<math>\Omega</math>

R_cable = 200 <math>\Omega</math>

R_path-diff¹ = 467<math>\Omega</math>

R_path-single¹ = 400<math>\Omega</math>

The reference-voltage noise is not taken into account.

¹: path refers to path-resistance in the mce crate

• Legacy opams used as TES bias output circuitry:

opamp	output type	DAC config	evpp@0.1-10Hz nV	en@0.1Hz nV/rtHz	en@10kHz nV/rtHz	in@0.1Hz pA/rtHz	in@10kHz pA/rtHz	en-shunt pV/rtHz	en-shunt @0.1Hz pV/rtHz
LT1128C	differential	unipolar	35	1.5	0.9	15	0.9	0.12	3.06
OPa227U	differential	unipolar	90	6.5	3	6.5	0.4	0.12	1.36
AD797	differential	bipolar	50	5.7	0.9	20*	2	0.46	11.24
AD8675	differential	bipolar	100	6.5	2.8	1	<0.3	0.30	0.79
AD8675	differential	unipolar	100	6.5	2.8	1	<0.3	0.12	0.38
AD8622	single-ended	unipolar	200	20	11	0.25	0.15	0.09	0.36
OP285	single-ended	unipolar	100	6.5	13.1	1	33.3	0.11	1.34
OP2227	single-ended	unipolar	90	6.5	3	6.5	0.4	0.06	0.75

Where

e_n: voltage noise at the output of the op-amp (independent of cable-resistance, etc)

i_n: output current noise partially driven from R_path

e_n-shunt: voltage noise at the shunt resistor