# Buffer

In this topic:

## Netlist entry

Axxxx in out model_name

## Connection details

 Name Description Flow Type in Input in d out Output out d

## Model format

.MODEL model_name d_buffer parameters

## Model parameters

 Name Description Type Default Limits rise_delay Rise delay real 1nS 1e-12 $- \infty$ fall_delay Fall delay real 1nS 1e-12 $- \infty$ stored_delay Stored delay (overrides rise_delay and fall_delay) real 0 $0 - \infty$ input_load Input load value (F) real 1pF none family Logic family string UNIV none in_family Input logic family string UNIV none out_family Output logic family string UNIV none out_res Digital output resistance real 100 $0 - \infty$ out_res_pos Digital output res. pos. slope real out_res $0 - \infty$ out_res_neg Digital output res. neg. slope out_res $0 - \infty$ open_c Open collector output boolean FALSE none min_sink Minimum sink current real -0.001 none max_source Maximum source current real 0.001 none sink_current Input sink current real 0 none source_current Input source current real 0 none open_e Open emitter output boolean FALSE none

## Device Operation

This device is a simple buffer with a single input and output. It can optionally be specified to have an open collector (open_c parameter) or open emitter (open_e parameter) output. Further, if the stored_delay parameter is specified, the device will act as a pure delay. This means that it will pass pulses that are shorter than the delay time whereas normally (delay specified by rise_delay and fall_delay) such pulse would be swallowed (stored_delay is also known as transport delay).

The following table describes the device operation in detail

 OPEN_C parameter OPEN_E parameter Input Output state Output strength FALSE FALSE 0 0 STRONG FALSE FALSE 1 1 STRONG FALSE FALSE UNKNOWN UNKNOWN STRONG FALSE TRUE 0 0 HI-IMPEDANCE FALSE TRUE 1 1 STRONG FALSE TRUE UNKNOWN UNKNOWN UNDETERMINED TRUE FALSE 0 0 STRONG TRUE FALSE 1 0 HI-IMPEDANCE TRUE FALSE UNKNOWN 0 UNDETERMINED TRUE TRUE 0 1 HI-IMPEDANCE TRUE TRUE 1 0 HI-IMPEDANCE TRUE TRUE UNKNOWN UNKNOWN UNDETERMINED
Note the difference between open emitter and open collector operation. These modes have been designed to be as close to as possible to real devices, in particular their behaviour into an open circuit. An open emitter output, when switching from high to low is likely to follow the voltage on the device's base due to the base-emitter capacitance so the output state follows the input state. An open collector (or open drain) output on the other hand will remain in the low state when its input switches.