579 FAST FILTER AMPLIFIER

• For fast timing with germanium and other semiconductor detectors
• Fast <8-ns rise time
• Independent integration and differentiation
• Gated baseline restorer
• Pole-zero cancellation
• 50-W delay cable clipping
• Voltage gain X0.9 to X500
• Output drives to ±5 V on a 50-W load

The ORTEC Model 579 wideband Fast-Filter Amplifier with gated baseline restorer (Fig. 1) enhances fast-timing measurements by improving the noise-to-slope ratio and providing ultra-high count rate spectroscopy capability.

A fast rise time (<8 ns), high output drive (±5 V into 50 W), and wide voltage gain range (X0.9–X500) make the Model 579 useful for many timing applications, including those utilizing low-gain photomultiplier tubes. The Model 579 is particularly suited for use with ORTEC Constant-Fraction Discriminators such as Models 583, 935, or 473A in timing applications with high- purity germanium (HPGe) or silicon charged-particle detectors (Figs. 2 and 9 and Tables 1 and 2). Excellent dc and gain stability (±50 µV/°C and ±0.05%/°C, respectively) eliminate the need for a dc level adjustment. A Busy LED and Busy Output are included to aid in BLR adjustment and system interfacing.

In addition, the wideband gated baseline restorer and pole-zero cancellation network permit ultra-high output counting rates. A wide variety of pulse filtering is available for improved signal processing. The Model 579 combines continuously variable gain, independently selectable integration and differentiation time constants (Out, 10, 20, 50, 100, 200, and 500 ns), and cable clipping capability (external cable delay), making this versatile unit an important asset for sophisticated time and energy spectroscopy.

Fig. 1   Block Diagram of the Model 579 Fast-Filter Amplifier.

Fig. 2  Timing Resolution FWHM and FW.1M as a
Funciton of Energy an Energy Window of ±50 keV.

Fig. 3  Model 579 output signals for t_D = Out
and t_i = Out, 10, 20, 50, 100, 200, and 500 ns.

Fig. 4  Model 579 output signals for t_i = Out
and t_D = Out, 10, 20, 50, 100, 200, and 500 ns.

Fig. 5  Example of Model 579 ultra-high count rate capability.
Input signal from a BNC random pulse generator at approximately
1 million counts per second. Fast-filter amplifier t_i = t_D = 500 ns.

Fig. 6 Model 579 output signals for t_i = t_D = Out at 1, 2, and 5 V.
 

Fig. 7   DC output offset vs. temperature measured on five typical units.

Fig. 8   Percentage gain shift vs. temperature measured on five typical units.

Fig. 9   Gamma-Gamma coincidence system using a
plastic scintillator and a large HPGe coaxial detector.

ORDERING INFORMATION