Prior to the OMC glass bench installation, the OMC DCPD preamps (D060572 SN004/005) were tested in the H2PSL enclosure.
The results are almost identical to the ones seen in LLO. Now the preamps are attached to the OMC suspension.

- Transimpedance measurement

This preamp uses a resister as a transimpedance (i.e. current to voltage conversion).
The transimpedance can be switched by a 5V relay with the "ZSwicth" terminal.
The resister values were read by a multimeter at the diode (between Cathode pin and GND pin).

Preamp SN004
ZSwitch=L 100.8 Ohm
ZSwitch=H 400.9 Ohm

Preamp SN005
ZSwitch=L 100.2 Ohm
ZSwitch=H 400.0 Ohm

- Transfer function measurement

The voltage transfer function of the preamps are measured by applying the source voltage
to the lead pins inserted to the PD connector. The source amplitude of 20mV was nominally applied.
For the linearity check (as per request by Keita), the measurement with a half amplitude (10mV) was
also done. ZSwicth does not change the transfer function as it only swicthes the transimpedance resisters.

Page 1 of the attached PDF: linearity check
The TFs with the 20mV and 10mV amplitudes matches in 1% in amplitude and 1deg in phase.

Page 2: Consistency check
Comparison with the circuit model (with nominal circuit parameters) by Zach Korth. The measured value is
consistent with the circuit model. Of course, they don't match perfectly as the actual circuit parameters are different from nominal.

Page 3: Empirical ZPK fit
For the modeling purpose, the TF with the 20mV excitation was fitted using liso. The fitting was done with precision
of 1% in amplitude and 1deg in phase. The list of poles, zeros, and gain is in the page. 

Page 4: Current noise 
The input-referred current noise was measured with the two impedance settiings. The noise expectations from LISO
model (by Zack Korth) is also shown. As seen in LLO, we have some discrepancy from the LISO model at the low and
high freq edge. For the low impedance (=high beam power) mode, we can see the shot noise level of 35mA photocurrent
between 12-100kHz.

Page 5-8: Same analysis for the preamp SN005