﻿ Hspice TUTORIAL

# SPIRO THE TECH GURU

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## Hspice TUTORIAL

Let us take a look at the following hspice code.

 ```* Stripline circuit .Tran 50ps 7.5ns .OPTION post Probe VIN 1 0 PWL 0 0v 250ps 0v 350ps 3.3v Rsource 1 2 50 Tfirst 2 0 3 0 ZO=50 TD=0.17ns *C2 3 0 2p Tsecond 3 0 4 0 ZO=50 TD=500ps Rtermination 4 0 50 .Probe v(1) v(2) v(3) v(4) .End```

Let us understand the elements of the code of hspice. The statement

* Stripline circuit

is a comment in hspice. Any line starting with * is taken as a comment. Use comments profusely to make your code more understandable.

The statement

.Tran 50ps 7.5ns

instructs hspice simulator to perform transient simulation analysis up to time period 7.5ns.

The statement

VIN 1 0 PWL 0 0v 250ps 0v 350ps 3.3v

Creates a piecewise linear voltage source. The voltage source is connected between nets named 1 and 0. The net 0 or GND is universally reserved for ground. At time t = 0, the level of voltage is 0v. At time t = 250 ps, the voltage level is 0v. At time t = 350 ps, the voltage level is 3.3v. This creates a voltage source with 0% to 100% rise time of 100 ps. The voltage rises between time 250 ps to 350 ps.

The statement

Rsource 1 2 50

connects a resistance of 50 ohm between net node 1 and net node 2. We therefore, have a voltage source with 50 ohm source resistance.

The statement

Tfirst 2 0 3 0 ZO=50 TD=0.17ns

Creates a transmission line connected between net node 2 and net node 3. The transmission line has a impedance of 50 ohms and delay of 0.17ns.

The statement

*C2 3 0 2p

is a comment. Had there been no * in the beginning it would have inserted a 2pf capacitor between net node 3 and ground.

The statement

Tsecond 3 0 4 0 ZO=50 TD=500ps

Again creates a transmission line of characteristic impedance 50 Ohms and length equivalent to a delay time of 500 ps.

We place a termination resistance of 50 Ohms, using the statement

Rtermination 4 0 50

Finally the statement

.Probe v(1) v(2) v(3) v(4)

is used to probe the voltage levels at nodes 1, 2, 3 and 4.