The Stanford Research Systems SR645 is a two-channel high-pass filter designed for precision signal processing and low-frequency noise rejection. Each channel operates independently with an 8-pole, 6-zero elliptic filter topology, enabling simultaneous processing of separate signals or stereo signal pairs. The instrument combines adjustable filtering with programmable gain stages, delivering up to 80 dB total gain and cutoff frequency control from 1 Hz to 100 kHz.
Technical Specifications
Filter Performance
• 8-pole, 6-zero elliptic topology with 115 dB/octave rolloff
• Stopband attenuation: >80 dB
• Passband ripple: 0.3 dB peak to peak (typical HPF)
• Cutoff frequency range: 1 Hz to 100 kHz with 3-digit resolution
• Programmable switching time: 300 Ω load
• Optional high-power output: 10 Vpp into 50 Ω load (Option 01)
• Adjustable DC offset
Performance Metrics
• Phase match between channels: ±0.75° DC to 100 kHz (typical); ±0.25° below 10 kHz
• Harmonic distortion: <–80 dB at 100 Hz; <–50 dB at 1 kHz
• Channel crosstalk: <–110 dB (source <50 Ω)
• Spurious components: <–80 dB (source <50 Ω)
• Filter bypass mode: 450 kHz bandwidth with gain stages active
– Key Features
• Independent bypass control for each filter channel
• Dual-channel phase matching for stereo applications
• Nine non-volatile memory locations for configuration storage
• Analog ground connector on rear panel for flexible grounding
– Typical Applications
Precision instrumentation, audio signal conditioning, dual-channel measurements requiring matched phase response, and AC coupling applications with adjustable gain.
– Compatibility & Integration
GPIB and RS-232 interfaces enable full remote control and parameter readout. Dimensions: 15.7" × 3.0" × 14.0"; weight: 12 lbs. Power: 45 W at 100/120/220/240 VAC, 50/60 Hz.
