NIM Model 428F Quad Linear Fan-In/Fan-Out

The LeCroy Model 428F Quad Linear Fan-In/Fan-Out combines the functions of two previously separate LeCroy linear circuits in one compact unit. Each of the Model 428F's four channels contains 4 direct-coupled linear bipolar inputs, a po- larity inversion switch, and four direct-coupled linear outputs. The bipolar inputs, together with the polarity switch, allow convenient summing of either anode or dynode pulses. An output swing of +100 mV to -2 volts is compatible with all normal analog inputs (e.g., discriminators, ADC'S, etc.) and also accommodates standard logic levels. Each of the Model 428F's inputs is provided LeCroy high- risk input protection circuitry which gives immunity to transient signals up to +/-5 A for 0.5 microsecond.

The incorporation of the polarity switch is particularly significant in that it enables convenient, direct use of the fanned-out dynode signals for multiple fast logic deci- sions, while the anode signal can be directly applied to a current-integrating ADC.

All outputs are reverse-terminated and mutually isolated. The Model 428F utilizes a direct-coupled feedback-stabilized circuit design that provides excellent linearity, long- term stability, and uniformity of gain and pulse shape. The speed of the unit is suitable for all common photomultiplier and logic signals, and there are no duty cycle limitations or rate effects in the Normal Mode.

In the Inverting Mode, the Model 428F operates as a capacitively-coupled unit with a 400 usec time constant, recovering to the average non-inverted DC input level. In addition, the Model 428F exhibits duty-factor-related baseline shifts equal to twice that of a normal AC-coupled circuit. Thus, although the Inverting Mode provides great versatility and convenience in application, some care must be exercised when using this mode with wide inputs or at high rates.

The Model 428F is packaged in a standard NIM #1 width module and utilizes +/-12 V, +/-24 V at little enough current to permit the use of 12 modules (48 channels) in a standard NIM power bin.

    SPECIFICATIONS
    NIM Model 428F
   QUAD LINEAR FAN-IN/FAN-OUT

 INPUT CHARACTERISTICS

 Number of Channels:  Four.

 Inputs:   4 per channel; 50 Ohm; direct-coupled in non-inverting mode. In inverting mode
   operates as a capacitively-coupled unit with a 400 usec time constant.

 Polarity:  Positive or negative.

 Reflection Coefficient:  Less than 7% for inputs of 2 nsec risetime.

 Input Protection:  Inputs protected against 0.5 usec transient overloads, up to +/- 5 A.


 OUTPUT CHARACTERISTICS

 Outputs:  4 per channel; reverse-terminated; direct-coupled; for optimum output shape,
   three outputs must be terminated into 50 Ohm. For proper operation, at least 2
   outputs must be terminated on each channel used.

 Integral Non-Linearity:  +/- 1 % up to - 1 volt.

 Linear Range:  Normal Mode: + 1 00 mV to > - 2 volts.
   Inverting Mode: +100 mV to > -1.5 volts.

 Maximum Amplitude:  Normal Mode: > -2.0 volts into 50 Ohm.
   Inverting Mode: > -1.5 volts into 50 Ohm.

 Risetimes and Falltimes: -- 2.5 nsec, 10% to 90%, with outputs terminated in 50Ohm.

 Gain:   Normal Mode: 1.0 +/- 2% up to -2 volts.
   Inverting Mode: Approximately 0.98 up to -1.5 volts.

 Duty Cycle Limitations:  None for direct-coupled outputs.

 DC Offset:  Adjustable with front-panel potentiometer. Care should be taken to readjust DC
   level whenever the Normal/Inverting switch is used.

 DC Offset Stability:  <60 /uV/'C in normal and inverting modes.

 Output DC Level Voltage
 Coefficient:  <25 uV/1% variation of any voltage in normal and inverting modes.

 Interchannel Isolation:  40 dB.

 Noise:   <750 uV rms.

 Stage Delay:  <6 nsec.

 Overload Recovery:  Approximately 2 nsec with four simultaneous NIM level (-800 mV) inputs).


 GENERAL

 Polarity Inversion:  A front-panel switch on each channel selects normal or inverting operation.

 Packaging:  RF-shielded AEC/NIM #1 module; dimensions 1.375 x 8.75 x 10 inches deep.
   Lemo-type connectors.

 Current Requirements:  +24 V at 80 mA, - 24 V at 80 mA, +12 V at 160 mA, -12 V at 160 mA.