Stanford Research Systems SR554 User Manual

Model SR554

Transformer Preamplifier

email: [e-mail] • www.thinkSRS.com

1290-D Reamwood Avenue

Sunnyvale, Califor nia 94089

Phone: [phone] • Fax: [phone]

Copyright © 1999 by SRS, I nc.

All Rights Re s e r v e d .

Revision 1.2 (10/2001)

SR554 SPECIFICATIONS

Input s Single ended or differential
Input Impedance 0.5 Ω
Maximum Inputs Transformer and Buffer: 14.0 mV RMS (±20 mV peak)

Transformer only: 350 mV RMS (±0.5 V peak)

Common Mode Range: ± 100 VDC

Rejection: 140 dB @ 100 Hz
Isolation > 40dB DC to 500 MHz
Input Noise 120 pV/√Hz @ 10 Hz (typical)

(Transformer and Buffer) 100 pV/√Hz @ 100 Hz

100 pV/√Hz @ 1000 Hz

(see noise contours, pg. 5)
Gain Transformer and Buffer: 500 (nominal)

Transformer only : 100 (nomi nal)

See Amplitude-Frequency Response Curve (pg 6).
Gain Accuracy 5% (with fixed source resistance)
Gain Stability 100 ppm/ °C
Outputs Single ended or differential
Output Impedance Transformer and Buffer: < 1.0 Ω

Transformer only: > 5000 Ω
Maximum Output Transformer and Buffer: 7.1 V RMS (10 Volts peak)

Transformer only: 35.3 V RMS (50 Volts peak)
Power Provided by any SRS lock-in amplifier via the supplied

connector cable or from a ± 20 volts DC @ 100 mA source.

Mechanical 2.9" X 3.8" X 7.5" (HxWxL), 4 lb.
Warranty One year parts and labor on materials and workmanship.

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OPERATION

The SR554 Transformer Preamplifier is
desig ned to be used with al l SRS Lock-in
amplifiers. It can reduce input noise of a
lock-in amplifier dramatically (as low as
100 pV/√Hz) and e xte nds the lock-in’s f ul l
scale sensitivity (without expand). It also
nearly elimi nates noi se radiated bac k f ro m
the lock-in amplifier to the users
experiment. When used as a remote
preamplif ier, t he SR554 ca n elimi nate t he
effects of noise pickup on long signal
cables. The SR554 transformer is
designed to be used with its internal
buffer, but the buffer may be by passe d fo r
transformer only operation. When used
as a simple transformer, no power
connection is required.

CONNECTING THE SR554

When the transformer and buff er are used
together, power is s upp lied to the SR554
via the 9 pin connector and cable. This
cable mates with all SRS lock-in amplifiers
through the rear panel connector. To use
the SR554 without an SRS lock-in, the
user must provide their own ±20 VDC
(100 mA) source. Always connect the
power ca ble to t he SR554 while t he loc k­in power is off. Attach one end of the
cable to the connecto r on the rear o f the
SR554, and connect the other e nd to t he
PRE-AMP connector on the rear of the
lock-in. If a longer cable is required, any
standard 9 pin cable will s uff ice since al l
connections are straight through. When
the lock-in power is on, the POWER

indicator on the SR554 will light.
The SR554 outp ut s witc h se lects bet ween

buffered mode with a gain of 500,
(transformer and buffer) or bypassed
mode with a gain of 100 (transformer
alone). In the buffered mode, the
transformer secondary goes into a low
noise buffer which drives the output cable.
This is to reduce loading due to the
transformer output impedance (about 5
kΩ) and c ab le c apaci tance (10's o f pf). If
the user prefers not to use the b uffer o r if
power is n’t avai lable f or the pre amp, t hen
the SR554 ca n be used i n the bypassed
mode. I n the bypass ed mo de, the outp ut
impedance of the pre-amp is 5 kΩ and
care must be taken to avoid loading the
output with too much cable capacitance.
Power should not be connected to the
SR554 when used in the bypass mode.

INPUT CONNECTION

Signals into the SR554 c an be co nnected
either single ended through t he (A ) input,
or differentially through the (A-B) inputs.
In the single ended configuration the
shield and center conductor of the (A)
input are connected to the transformer.
For differential connection, the shields of
the input BNC’s are connected to the
SR554 case and the (A) and (B) center
conductors connect to the transformer.

The input i mpedance is a combination of

0.5 Ω and 0.5 H (i n se ries) i n para llel wit h

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