SRS Labs SR445A User Manual

MODEL SR445A

350 MHz PREAMPLIFIER

MODEL SR445A

350 MHz PREAMPLIFIER

Phone: [phone] • Fax: [phone]

email: [e-mail] • www.thinkSRS.com

1290-D Reamwood Avenue

Sunnyvale, California 94089

Copyright © 2004 by SRS, Inc.

All Rights Reserved.

Revision 1.1 (03/2006)

Certification

Stanford Research Systems certifies that this product met its published specifications at
the time of shipment.

Warranty

This Stanford Research Systems product is warranted against defects in materials and
workmanship for a period of one (1) year from the date of shipment.

Service

For warranty service or repair, this product must be returned to a Stanford Research
Systems authorized service facility. Contact Stanford Research Systems or an authorized
representative before returning this product for repair.

Information in this document is subject to change without notice.

Copyright © Stanford Research Systems, Inc., 2004. All rights reserved.

Stanford Research Systems, Inc.
1290-C Reamwood Avenue
Sunnyvale, California 94089
Phone: [phone] • Fax: [phone]

www.thinkSRS.com • e-mail: [e-mail]

Printed in U.S.A.

SR445A Quad Fast Amplifier

Description

The SR445A is a four-channel, 350MHz bandwidth, dc coupled, 50Ω amplifier with a
gain of 5× (or +14dB) in a half-width 1U chassis. Two, three or four channels may be
cascaded for gains of 25×, 125×, or 625×, (+28dB, +42dB, or +56dB.) The unit uses
BNC connectors for inputs and outputs. The unit is powered from the ac mains by a
universal input power supply.

The full scale input is ±200mV. The input noise is typically 5.2nV/√Hz. The output is
linear over ±1V and should be terminated into a 50Ω load. Output rise and fall times are

1.3ns. The output will recover from a 10× full scale overload in 3ns. The unit is protected
from ±50V, 1µs input overloads.

There are five LEDs on the front panel; one indicates that the unit is powered and “on”
and four indicate when the output signal for the corresponding channel is outside its
linear range, typically ±1.3Vdc. Brief overloads (<5ns) trigger a 10ms flash.

Operation

The input impedance for each channel is 50Ω. (There is a front panel switch that allows
the input resistance of Channel 1 to be set to either 500Ω or 50Ω. The 500Ω setting
provides high transimpedance gain for current source—such as photomultiplier tubes—
that may be useful when the amplifier is located close to the signal source.) The dc input
voltage must be limited to ±4V to avoid damaging the amplifier front-end. The amplifier
is internally protected from 50V transients of 1µS duration. The 50Ω input impedance is
intended to terminate 50Ω coaxial cable such as RG-58.

The amplifiers perform well when cascaded due to their high input return loss and flat
frequency response characteristics. Referenced to the input, the broadband noise (1Hz to
300MHz) is 80µV
expect to see about 10mV
output of three cascaded amplifiers, and 250mV

. Peak-to-peak noise is typically 5× the RMS value and so one would

rms

at the output of two cascaded amplifiers, 50mVpp at the

pp

at the output of four cascaded

pp

amplifiers.

SR445A Specifications

Specification Min Typ Max Units

Inputs (driven by 50Ω source)

Input signal level -200 +200 mV
Impedance 49.5 50 50.5 Ω
Return loss 32 dB
Offset -500 0 +500 µV
Offset drift -10 +10 µV/°C
Bias current (note 1) 3 10 µA
Protection (dc) -4 +4 Vdc
Protection (1µS transient) -50 +50 V
Recovery time (10×FS overload) 3 nS
Noise (10Hz) 22 nV/√Hz
Noise (100Hz) 8.6 nV/√Hz
Noise (> 1kHz) 5.2 nV/√Hz
Noise (1Hz to 300MHz BW) 80 µVrms
Crosstalk (CH1 out to CH2 in) -61 dB
Crosstalk (CH2 out to CH1 in) -82 dB

Amplifier

Gain (note 2) 4.95 5.00 5.05 V/V
Bandwidth (-3dB) 350 MHz
Rise/fall time 1.3 nS
Propagation delay 2.7 nS

Outputs (driving 50Ω)

Source impedance (note 3) 49.5 50 50.5 Ω
Linear operation -1.0 +1.0 V
Overload level -1.3 +1.3 V
Limit level -1.6 +1.6 V

General

Number of Channels 4
Operating temperature 0 40 ºC
Mains voltage 90-132 175-264 Vac
Mains power 15 Watts
Mains frequency 47 63 Hz
Dimensions 8.35” 1.70” 8.10” W×H×D

Notes:

1. The input bias current flows out of the unit, creating a positive offset of about 150µV on the 50Ω

input termination. This offset will be affected by the dc impedance of the source that is connected
to the input.

2. Amplifier gain is calibrated by applying a known current to the input and measuring the voltage
into a high impedance load. The gain is adjusted so that a 1mA source applied to the input
produces a 500mV voltage at the unloaded output.

3. Channel 1 may be set to either 500Ω or 50.5Ω via a front panel switch.