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Merged
Nimok15 merged 1 commit into from
Jun 25, 2026
Merged

Update low_voltage_cmirror.spice #8

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22 changes: 13 additions & 9 deletions tests/sim/testbenches/low_voltage_cmirror.spice
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Original file line number Diff line number Diff line change
@@ -1,8 +1,8 @@
* Testbench: low-voltage cascode current mirror
* low_voltage_cmirror ports: IBIAS1 IBIAS2 GND IOUT1 IOUT2
* IBIAS1 is the reference input node; IBIAS2 is an internally-generated
* second-tier bias (left to float to its own operating point); IOUT1/IOUT2
* are the two mirrored output branches.
* subckt name: Low_voltage_current_mirror (filename stem is low_voltage_cmirror)
* ports: IBIAS1 IBIAS2 GND IOUT1 IOUT2
* IBIAS1 and IBIAS2 are BOTH reference-current inputs (main + cascode bias);
* IOUT1/IOUT2 are the two mirrored output branches.
*
* Functional check: push a reference current into IBIAS1 and confirm both
* output branches sink ~the same current (1:1 mirror) when held at mid-rail.
Expand All @@ -13,17 +13,21 @@
* point is delicate -- calibrate the check bands against a golden ngspice run.
.param VDD=1.8
.param IREF=10u
* Reference current into the IBIAS1 node.
Iref 0 IBIAS1 DC {IREF}
* This cell has TWO bias-current inputs: IBIAS1 (main mirror) and IBIAS2
* (cascode level -- it is the Ib node of the second FVF and gates X4/X5).
* Both must be driven, or the output cascodes are starved and sink ~0.
* IBIAS2's value sets the cascode bias and may need a different magnitude
* than IREF -- calibrate against a golden run.
Iref 0 IBIAS1 DC {IREF}
Iref2 0 IBIAS2 DC {IREF}
* Outputs held near mid-rail through ammeters; i(vmX) is the sunk mirror current.
Vsup DD 0 DC 0.9
Vm1 DD IOUT1 DC 0
Vm2 DD IOUT2 DC 0
* DUT: IBIAS1 IBIAS2 GND IOUT1 IOUT2
* GND port tied straight to node 0 (no source -- a 0 V source here both ends
* on ground reads as a shorted VSRC and aborts the analysis). IBIAS2 left on
* its own net.
X1 IBIAS1 net_ibias2 0 IOUT1 IOUT2 low_voltage_cmirror
* on ground reads as a shorted VSRC and aborts the analysis).
X1 IBIAS1 IBIAS2 0 IOUT1 IOUT2 Low_voltage_current_mirror
.dc Iref 2u 20u 1u
.measure dc iout1_op FIND i(vm1) AT=10u
.measure dc iout2_op FIND i(vm2) AT=10u
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