From b041f8c105b16bd1b5475ab6e9b335d54b99102e Mon Sep 17 00:00:00 2001
From: Paul Falstad <paul@falstad.com>
Date: Sun, 27 Oct 2024 14:21:07 -0700
Subject: [PATCH] fix schmitt trigger bad behavior with nonlinear circuits
 (#104)

---
 src/com/lushprojects/circuitjs1/client/SchmittElm.java | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/com/lushprojects/circuitjs1/client/SchmittElm.java b/src/com/lushprojects/circuitjs1/client/SchmittElm.java
index 9b639516c..ce1edfc54 100644
--- a/src/com/lushprojects/circuitjs1/client/SchmittElm.java
+++ b/src/com/lushprojects/circuitjs1/client/SchmittElm.java
@@ -31,8 +31,13 @@ public SchmittElm(int xa, int ya, int xb, int yb, int f,
 	}
 
 	int getDumpType() { return 182; }
+
+	double lastOutputVoltage;
+
+	void startIteration() {
+	    lastOutputVoltage = volts[1];
+	}
 	void doStep() {
-	    double v0 = volts[1];
 	    double out;
 		if(state)
 		{//Output is high
@@ -60,7 +65,7 @@ void doStep() {
 		}
 	    
 	    double maxStep = slewRate * sim.timeStep * 1e9;
-	    out = Math.max(Math.min(v0+maxStep, out), v0-maxStep);
+	    out = Math.max(Math.min(lastOutputVoltage+maxStep, out), lastOutputVoltage-maxStep);
 	    sim.updateVoltageSource(0, nodes[1], voltSource, out);
 	}