V. Voltage Source
Symbol Names: VOLTAGE, BATTERY
Syntax: Vxxx n+ n- <voltage> [AC=<amplitude>] [Rser=<value>] [Cpar=<value>]
This element sources a constant voltage between nodes n+ and n-. For AC analysis, the value of AC is used as the amplitude of the source at the analysis frequency. A series resistance and parallel capacitance can be defined. The equivalent circuit is:
Voltage sources have historically been used as the current meters in SPICE and are used as current sensors for current-controlled elements. If Rser is specified, the voltage source can not be used as a sense element for F, H, or W elements. However, the current of any circuit element, including the voltage source, can be plotted.
Syntax: Vxxx n+ n- PULSE(V1 V2 Tdelay Trise Tfall Ton Tperiod Ncycles)
Time-dependent pulsed voltage source
| Name | Description | Units |
| Voff | Initial value | V |
| Von | Pulsed value | V |
| Tdelay | Delay | sec |
| Tr | Rise time | sec |
| Tf | Fall time | sec |
| Ton | On time | sec |
| Tperiod | Period | sec |
| Ncycles | Number of cycles(Omit for free-running pulse function) | cycles |
Syntax: Vxxx n+ n- SINE(Voffset Vamp Freq Td Theta Phi Ncycles)
Time-dependent sine wave voltage source.
| Name | Description | Units |
| Voffset | DC offset | V |
| Vamp | Amplitude | V |
| Freq | Frequency | Hz |
| Td | Delay | sec |
| Theta | Damping factor | 1/sec |
| Phi | Phase of sine wave | degrees |
| Ncycles | Number of cycles(Omit for free-running sine function) | cycles |
For times less than Td, the output voltage is given by
Voffset+Vamp*sin(p*Phi/180)
For times after Td, but before Ncycles have completed, the voltage is given by
Voffset+Vamp*exp(-(time-Td)*Theta)*sin(2*p*Freq*(time-Td)+p*Phi/180)
For times after Ncycles have completed, the voltage is the last voltage when Ncycles completed. Note Ncycles does not have to be an integer.
The damping factor, Theta, is the reciprocal of the decay time constant.
Syntax: Vxxx n+ n- EXP(V1 V2 Td1 Tau1 Td2 Tau2)
Time-dependent exponential voltage source
| Name | Description | Units |
| V1 | Initial value | V |
| V2 | Pulsed value | V |
| Td1 | Rise delay time | sec |
| Tau1 | Rise-time constant | sec |
| Td2 | Fall delay time | sec |
| Tau2 | Fall-time constant | sec |
For times less than Td1, the output voltage is V1. For times between Td1 and Td2 the voltage is given by
V1+(V2-V1)*(1-exp(-(time-Td1)/Tau1))
For times after Td2 the voltage is given by
V1+(V2-V1)*(1-exp(-(time-Td1)/Tau1))-(V2-V1)*(1-exp(-(time-Td2)/Tau2))
Syntax: Vxxx n+ n- SFFM(Voff Vamp Fcar MDI Fsig)
Time-dependent single frequency FM voltage source.
| Name | Description | Units |
| Voff | DC offset | V |
| Vamp | Amplitude | V |
| Fcar | Carrier frequency | Hz |
| MDI | Modulation index | - |
| Fsig | Signal frequency | Hz |
The voltage is given by
Voff+Vamp*sin((2.*p*Fcar*time)+MDI*sin(2.*p*Fsig*time))
Syntax: Vxxx n+ n- PWL(t1 v1 t2 v2 t3 v3...)
Arbitrary Piece-wise linear voltage source.
For times before t1, the voltage is v1. For times between t1 and t2, the voltage varies linearly between v1 and v2. There can be any number of time, voltage points given. For times after the last time, the voltage is the last voltage.
Syntax: Vxxx n+ n- wavefile=<filename> [chan=<nnn>]
This allows a .wav file to be used as an input to LTspice. <filename> is either a full, absolute path for the .wav file or a relative path computed from the directory containing the simulation schematic or netlist. Double quotes may be used to specify a path containing spaces. The .wav file may contain up to 65536 channels, numbered 0 to 65535. Chan may be set to specify which channel is used. By default, the first channel, number 0, is used. The .wav file is interpreted as having a full scale range from -1V to 1V.
This source only has meaning in a .tran analysis.