The Stanford Research Systems SR445A is a four-channel preamplifier delivering DC to 350 MHz bandwidth with 1 ns rise/fall time and 6.4 nV/√Hz input noise. Each channel provides 5× voltage gain with cascaded gain up to 625×, making it ideal for low-level signal amplification in fast transient measurements. Dual complementary outputs per channel enable both inverting and non-inverting signal routing. Independent per-channel offset adjustment and selectable input impedance on channel 1 (50 Ω standard, switchable to ~500 Ω) accommodate diverse signal conditioning requirements. The unit features excellent phase linearity, -60 dB crosstalk isolation, and rapid 3 ns overload recovery for 10× overdrive conditions. Input protection tolerates ±50 V transients under 1 µs; outputs clamp at ±1.6 V with overload detection at ±1.3 V.
Technical Specifications
• Bandwidth: DC to 350 MHz (-3 dB)
• Channels: 4 independent
• Voltage Gain: 5× per channel; up to 625× cascaded
• Rise/Fall Time: 1 ns
• Input Noise: 6.4 nV/√Hz
• Input Impedance: 50 Ω standard; ~500 Ω selectable on channel 1
• Output Impedance: 50 Ω
• Propagation Delay: 2.7 ns per channel
• Crosstalk: -60 dB
• Overload Recovery Time: 3 ns (10× overload)
• Input Protection: ±50 V for <1 µs
• Output Clamp: ±1.6 V
• Output Overload Detect: ±1.3 V
• Phase Linearity: Excellent
• DC Accuracy: Excellent
• Power Consumption: 10 W
• AC Input: 100/120/220/240 VAC, 50/60 Hz
• Operating Temperature: 0 °C to 40 °C, non-condensing
• Form Factor: Single-width NIM crate standard
• Dimensions: 8.3" × 1.5" × 8.0" (WHD)
– Key Features
• Dual complementary 50 Ω BNC outputs per channel (inverting and non-inverting)
• DC-coupled 50 Ω BNC input connectors
• Independent per-channel offset adjustment
• Front-panel input impedance selection on channel 1
– Typical Applications
• Photomultiplier tube (PMT) and microchannel plate signal conditioning
• Fast photodiode amplification
• Photon counting and time-of-flight measurements
• Fast-timing experiments
• Oscilloscope, spectrum analyzer, and photon counter sensitivity enhancement
• High-speed digital system signal-to-noise optimization
• Laboratory pulsed signal measurement systems
– Compatibility & Integration
The SR445A mounts in standard NIM crate systems and requires an SR445 DC Power Supply/Preamplifier Mainframe for operation. Signal connections use standard BNC coaxial cables. Power delivery via DB-9 or 2-pin mini connector supplies ±12 VDC, +5 VDC, and ground (±15 V DC on certain models).
