The -ECL Trigger Level Option

Standard Triggering, without the -ECL Option

Most (but not all) Avtech pulse generators offer the standard ability to trigger from an external TTL pulse. TTL logic levels are LOW = 0V and HIGH = +3V to +5V, approximately. The trigger input is normally terminated inside the pulse generator with a relatively high impedance (470 Ohms or higher), to allow normal TTL logic ICs to drive the input. TTL logic levels and the normal termination method are shown below:

Triggering with the -ECL option

Models with the -ECL option trigger from different logic levels (LOW = -1.6V and HIGH = -0.8V), and have a different internal termination scheme (a 51 Ohm resistor to -2 Volts). This is illustrated below:

Most ECL ICs can drive this unusual termination. The use of a 51 Ohm impedance minimizes transmission line reflections. Models with the -ECL option will trigger only from ECL levels - they will not trigger from TTL levels.

Most instrument can be adapted to trigger from other levels, if required for a special applications. Contact Avtech with your special requirement!