CR-200-250NS

CR-200 Gaussian shaping amplifier (Rev. 2): General Description The CR-200 is a single channel shaping amplifier, intended to be used to read out the signals from charge sensitive preamplifiers (e.g. Cremat CR-110 or equivalent). Gaussian shaping amplifiers (also known as pulse amplifiers, linear amplifiers, or spectroscopy amplifiers) accept a step-like input pulse and produce an output pulse shaped like a Gaussian function. The purposes of this are to filter much of the noise from the signal of interest and to provide a quickly restored baseline to allow high counting rates. The CR-200 is available in 4 different shaping times: 100 ns, 250 ns, 1 s, and 4 s. Each has a fixed gain of 10. If additional gain is desired, it is recommended that this be done with the application of an additional amplifier between the preamplifier and the CR-200 shaping amplifier. Cremat offers an evaluation board (CR-160) which includes a variable gain amplifier of appropriate bandwidth, as well as all necessary connectors. Equivalent circuit diagram application guide Figure 3 shows an equivalent circuit. Pin numbers corresponding with the CR-200 preamplifier are shown. Input components Cin and Rin form a differentiating circuit. The following circuitry consists of two Sallen and Key filters, providing 4 poles of integration and signal gain. The numerous integration stages produce an output pulse that approximates a Gaussian function. Cin 1 8 2 Rin 3, 6, 7 Figure 3. part number Cin 470 pF 1000 pF 1000 pF 3300 pF Rin 220 240 1.0 k 1.2 k shaping time 100 ns 250 ns 1.0 s 4.0 s 100 mV CR-200-100ns CR-200-250ns CR-200-1 s CR-200-4 s 1.0 V input pulse shape output pulse shape Typical Application Figure 4 shows the CR-200 in a typical application, coupled to a detector via a CR-110 charge sensitive preamplifier. Depending on the requirements of your application, an ACcoupled amplifier may be added between the preamplifier and shaping amplifier to further increase the signal size. Det bias Figure 1. Comparison of sample input and output pulse shapes Improvements in Revision 2 The new CR-200 'Revision 2' has been improved with a significant reduction in power consumption, reduced output offset, and an improved thermal coefficient of output offset. Revision 2 is pin-for-pin compatible with the previous revision of CR-200, however it should be noted that the labeling has been changed so that pin 1 appears on the left side of the label. Definition of "Shaping Time" charge preamplifier filtered bias shaping amplifier CR-110 detector 12345678 CR-200 12345678 broadband amplifier input output +Vpower -Vpower +Vpower -Vpower The shaping time is defined as the time-equivalent of the "standard deviation" of the Gaussian output pulse. A simpler measurement to make in the laboratory is the full width of the pulse at half of it's maximum value (FWHM). This value is greater than the shaping time by a factor of 2.35. For example, a Gaussian shaping amplifier with a shaping time of 1.0 s would have a FWHM of 2.35 s. Pole/Zero Correction The decay time of the input pulse creates an offset in the baseline of the output pulse unless a pole/zero correction is utilized. This can be done by connecting a resistor between pin 1 (input) and pin 2 (P/Z). If the CR-200 is used to read out the Cremat CR-110 preamplifier, then this resistor value should be 300 k (CR-200-100ns), 130 k (CR-200250ns and CR-200-1 s), and 43 k (CR-200-4 s). If a different preamplifier is used, then the resistor value should be chosen so that it is equal to the decay constant (RC) of the preamplifier pulse divided by the CR-200 shaping amplifier input capacitor Cin (see table). Package Specifications The CR-200 circuit is contacted via an 8-pin SIP connection (0.100" spacing). Pin 1 is marked with a white dot for identification. P/Z Figure 4. Assume temp =20˚C, Vs = 9V, unloaded output CR-200 amplification channels gain polarity operating temperature range input noise voltage CR-200-100ns CR-200-250ns CR-200-1 s CR-200-4 s output impedance output offset output temperature coefficient power supply voltage (Vs) maximum minimum power supply current maximum output current (with loaded output) maximum output swing units 1 10 non-inverting -40 C to 85 C 90 90 45 30