tests/regression/misc, check resistor flicker noise

tests/regression/misc/Makefile.am

@@ -1,7 +1,7 @@
 ## Process this file with automake to produce Makefile.in
 
 
-TESTS = bugs-1.cir bugs-2.cir dollar-1.cir empty-1.cir resume-1.cir log-functions-1.cir alter-vec.cir
+TESTS = bugs-1.cir bugs-2.cir dollar-1.cir empty-1.cir resume-1.cir log-functions-1.cir alter-vec.cir test-noise-2.cir test-noise-3.cir
 
 TESTS_ENVIRONMENT = ngspice_vpath=$(srcdir) $(SHELL) $(top_srcdir)/tests/bin/check.sh $(top_builddir)/src/ngspice
 

tests/regression/misc/test-noise-2.cir

@@ -0,0 +1,49 @@
+Paolo's carbon resistor noise (Motchenbacher p. 290)
+* (exec-spice "ngspice %s" t)
+*
+* check whether resistor flicker noise behaves as expected
+
+.temp 25
+
+i1 1 0 dc 1e-3
+r1 1 2 1k rmodel l=1u w=10u
+v1 2 0 dc 0 ac 1
+
+.model rmodel r tc1=0.01 kf=100e-18 af=1.1
++ dlr=0.01u dw=0.01u
++ tnom=25
+
+.control
+
+* output noise in v/sqrt(Hz)
+compose wanted_onoise values 2.2637m 1.7981m 1.4283m 1.1345m 901.2011u 715.8494u 568.6194u 451.6705u 358.7746u 284.9848u 226.3715u
+
+* equivalent input noise in v/sqrt(Hz)
+*   extern_onoise / H
+let wanted_inoise = wanted_onoise
+
+noise v(1) v1 dec 5 1k 100k
+
+setplot noise2
+*print all
+
+setplot noise1
+*print onoise_spectrum wanted_onoise
+*print inoise_spectrum wanted_inoise
+
+let inoise_relerr = vecmax(abs(inoise_spectrum / wanted_inoise - 1))
+let onoise_relerr = vecmax(abs(onoise_spectrum / wanted_onoise - 1))
+
+echo "Note: relative inoise_relerr = $&inoise_relerr"
+echo "Note: relative onoise_relerr = $&onoise_relerr"
+
+if inoise_relerr > 1e-4 or onoise_relerr > 1e-4
+  echo "ERROR: test failed"
+  quit 1
+else
+  echo "INFO: success"
+  quit 0
+end
+
+.endc
+.end

tests/regression/misc/test-noise-2.out

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+INFO: success

tests/regression/misc/test-noise-3.cir

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+compare a m=2 resistor with two parallel instances
+* The expectation is identical inoise and onoise
+* (exec-spice "ngspice %s" t)
+
+.temp 25
+
+i1 1 0 dc 10ma ac=1
+r1 1 0 100 rmodel l=1u w=10u m=2
+
+i2  2 0 dc 10mA ac=1
+r2a 2 0 100 rmodel l=1u w=10u
+r2b 2 0 100 rmodel l=1u w=10u
+
+.model rmodel r kf=100e-18 af=1.1
++ dlr=0.01u dw=0.01u
+
+.control
+
+noise v(1) i1 dec 5 1k 100k
+print all
+
+noise v(2) i2 dec 5 1k 100k
+print all
+
+let relerr = noise4.onoise_total / noise2.onoise_total - 1
+
+echo "Note: relative relerr = $&relerr"
+
+if abs(relerr) > 1e-6
+  echo "ERROR: test failed"
+  quit 1
+else
+  echo "INFO: success"
+  quit 0
+end
+
+.endc
+.end

tests/regression/misc/test-noise-3.out

@@ -0,0 +1 @@
+INFO: success