update to schematic tool

js/cktsim.js

@@ -97,9 +97,11 @@ cktsim = (function() {
 	// load circuit from JSON netlist (see schematic.js)
 	Circuit.prototype.load_netlist = function(netlist) {
 	    // set up mapping for ground node always called '0' in JSON netlist
-	    this.node_map['0'] = this.gnd_node();
+	    var gnd_label = '0';
+	    this.node_map[gnd_label] = this.gnd_node();
 
 	    // process each component in the JSON netlist (see schematic.js for format)
+	    var found_ground = false;
 	    for (var i = netlist.length - 1; i >= 0; --i) {
 		var component = netlist[i];
 		var type = component[0];
@@ -118,6 +120,7 @@ cktsim = (function() {
 		var connections = component[3];
 		for (var j = connections.length - 1; j >= 0; --j) {
 		    var node = connections[j];
+		    if(node == gnd_label) found_ground = true;
 		    var index = this.node_map[node];
 		    if (index == undefined) index = this.node(node,T_VOLTAGE);
 		    connections[j] = index;
@@ -137,12 +140,18 @@ cktsim = (function() {
 		else if (type == 'i') 	// current source
 		    this.i(connections[0],connections[1],properties['value'],name);
 		else if (type == 'o') 	// op amp
-		    this.opamp(connections[0],connections[1],connections[2],properties['A'],name);
+		    this.opamp(connections[0],connections[1],connections[2],connections[3],properties['A'],name);
 		else if (type == 'n') 	// n fet
 		    this.n(connections[0],connections[1],connections[2],properties['W/L'],name);
 		else if (type == 'p') 	// p fet
 		    this.p(connections[0],connections[1],connections[2],properties['W/L'],name);
 	    }
+	    if(found_ground == false) { // No ground on schematic
+		alert('Please make at least one connection to ground  (inverted T symbol)');
+		return false;
+	    }
+	    return true;
+	    
 	}
 
 	// if converges: updates this.solution, this.soln_max, returns iter count
@@ -187,6 +196,8 @@ cktsim = (function() {
 
 	// DC analysis
 	Circuit.prototype.dc = function() {
+
+	    // Allocation matrices for linear part, etc.
 	    this.finalize();
 
 	    // Load up the linear part.
@@ -624,6 +635,17 @@ cktsim = (function() {
 	    return this.add_device(d, name);
 	}
 
+        Circuit.prototype.opamp = function(np,nn,no,ng,A,name) {
+	    // try to convert string value into numeric value, barf if we can't
+	    if ((typeof A) == 'string') {
+		ratio = parse_number(A,undefined);
+		if (A === undefined) return undefined;
+	    }
+	    var branch = this.node(undefined,T_CURRENT);
+	    var d = new Opamp(np,nn,no,ng,branch,A,name);
+	    return this.add_device(d, name);
+	}
+
         Circuit.prototype.n = function(d,g,s, ratio, name) {
 	    // try to convert string value into numeric value, barf if we can't
 	    if ((typeof ratio) == 'string') {
@@ -1090,6 +1112,15 @@ cktsim = (function() {
 		src.value = function(t) { return v; }  // closure
 	    }
 
+	    // post-processing for impulse sources
+	    // impulse(height,width)
+	    else if (src.fun == 'impulse') {
+		var h = arg_value(src.args,0,1);  // default height: 1
+		var w = Math.abs(arg_value(src.args,2,1e-9));  // default width: 1ns
+		src.args = [h,w];  // remember any defaulted values
+		pwl_source(src,[0,0,w/2,h,w,0],false);
+	    }
+
 	    // post-processing for step sources
 	    // step(v_init,v_plateau,t_delay,t_rise)
 	    else if (src.fun == 'step') {
@@ -1263,8 +1294,8 @@ cktsim = (function() {
 	    // MNA stamp for independent voltage source
 	    ckt.add_to_Gl(this.branch,this.npos,1.0);
 	    ckt.add_to_Gl(this.branch,this.nneg,-1.0);
-	    ckt.add_to_Gl(this.npos,this.branch,1.0);
-	    ckt.add_to_Gl(this.nneg,this.branch,-1.0);
+	    ckt.add_to_Gl(this.npos,this.branch,-1.0);
+	    ckt.add_to_Gl(this.nneg,this.branch,1.0);
 	}
 
 	// Source voltage added to b.
@@ -1448,9 +1479,9 @@ cktsim = (function() {
 	    // MNA stamp for inductor linear part
 	    // L on diag of C because L di/dt = v(n1) - v(n2)
 	    ckt.add_to_Gl(this.n1,this.branch,1);
-	    ckt.add_to_Gl(this.branch,this.n1,1);
+	    ckt.add_to_Gl(this.branch,this.n1,-1);
 	    ckt.add_to_Gl(this.n2,this.branch,-1);
-	    ckt.add_to_Gl(this.branch,this.n2,-1);
+	    ckt.add_to_Gl(this.branch,this.n2,1);
 	    ckt.add_to_C(this.branch,this.branch,this.value)
 	}
 
@@ -1464,6 +1495,51 @@ cktsim = (function() {
 	Inductor.prototype.load_tran = function(ckt) {
 	}
 
+
+
+	///////////////////////////////////////////////////////////////////////////////
+	//
+	//  Simple Voltage-Controlled Voltage Source Op Amp model 
+	//
+	///////////////////////////////////////////////////////////////////////////////
+
+        function Opamp(np,nn,no,ng,branch,A,name) {
+	    Device.call(this);
+	    this.np = np;
+	    this.nn = nn;
+	    this.no = no;
+	    this.ng = ng;
+	    this.branch = branch;
+	    this.gain = A;
+	    this.name = name;
+	}
+
+	Opamp.prototype = new Device();
+        Opamp.prototype.constructor = Opamp;
+        
+        Opamp.prototype.load_linear = function(ckt) {
+            // MNA stamp for VCVS: 1/A(v(no) - v(ng)) - (v(np)-v(nn))) = 0.
+	    var invA = 1.0/this.gain;
+	    ckt.add_to_Gl(this.no,this.branch,1);
+	    ckt.add_to_Gl(this.ng,this.branch,-1);
+	    ckt.add_to_Gl(this.branch,this.no,-invA);
+	    ckt.add_to_Gl(this.branch,this.ng,invA);
+	    ckt.add_to_Gl(this.branch,this.np,1);
+	    ckt.add_to_Gl(this.branch,this.nn,-1);
+	}
+
+	Opamp.prototype.load_dc = function(ckt,soln,rhs) {
+	    // Op-amp is linear.
+	}
+
+	Opamp.prototype.load_ac = function(ckt) {
+	}
+
+	Opamp.prototype.load_tran = function(ckt) {
+	}
+
+
+
 	///////////////////////////////////////////////////////////////////////////////
 	//
 	//  Simplified MOS FET with no bulk connection and no body effect.

js/schematic.js

@@ -634,9 +634,10 @@ schematic = (function() {
 
 	    // create a circuit from the netlist
 	    var ckt = new cktsim.Circuit();
-	    ckt.load_netlist(netlist);
-
-	    return ckt;
+	    if (ckt.load_netlist(netlist))
+		return ckt;
+	    else
+		return null;
 	}
 
 	Schematic.prototype.dc_analysis = function() {
@@ -645,6 +646,7 @@ schematic = (function() {
 	    this.redraw_background();
 
 	    var ckt = this.extract_circuit();
+	    if (ckt === null) return;
     
 	    // run the analysis
 	    this.operating_point = ckt.dc();
@@ -712,6 +714,7 @@ schematic = (function() {
 	Schematic.prototype.ac_analysis = function(npts,fstart,fstop,ac_source_name) {
 	    // run the analysis
 	    var ckt = this.extract_circuit();
+	    if (ckt === null) return;
 	    var results = ckt.ac(npts,fstart,fstop,ac_source_name);
 
 	    // save a copy of the results for submission
@@ -731,11 +734,28 @@ schematic = (function() {
 		var y_values = [];  // list of [color, result_array]
 		var probes = this.find_probes();
 
+		var probe_maxv = [];
+		var probe_color = [];
+
+		// Check for proble with near zero transfer function and warn
 		for (var i = probes.length - 1; i >= 0; --i) {
-		    var color = probes[i][0];
+		    probe_color[i] = probes[i][0];
 		    var label = probes[i][1];
 		    var v = results[label];
+		    probe_maxv[i] = array_max(v); // magnitudes always > 0
+		}
+		var all_max = array_max(probe_maxv);
+		for (var i = probes.length - 1; i >= 0; --i) {
+		    if ((probe_maxv[i] / all_max) < 1.0e-10) {
+			alert('Near zero ac response, remove ' + probe_color[i] + ' probe');
+			return;
+		    }
+		}
 
+		for (var i = probes.length - 1; i >= 0; --i) {
+		    var color = probes[i][0];
+		    var label = probes[i][1];
+		    var v = results[label];
 		    // convert values into dB relative to source amplitude
 		    var v_max = 1;
 		    for (var j = v.length - 1; j >= 0; --j)
@@ -774,6 +794,8 @@ schematic = (function() {
 	    this.dialog('Transient Analysis',content,function(content) {
 		    var sch = content.sch;
 		    var ckt = sch.extract_circuit();
+		    if (ckt === null) return;
+
 
 		    // retrieve parameters, remember for next time
 		    sch.tran_npts = content.fields[npts_lbl].value;
@@ -1943,25 +1965,27 @@ schematic = (function() {
 		var x1 = (index == 0) ? x_values[0] : x_values[index-1];
 		var x2 = x_values[index];
 
-		// for each plot, interpolate and output value at intersection with marker
-		c.textAlign = 'left';
-		var tx = graph.left_margin + 4;
-		var ty = graph.top_margin;
-		for (var plot = 0; plot < graph.y_values.length; plot++) {
-		    var values = graph.y_values[plot][1];
-
-		    // interpolate signal value at graph_x using values[index-1] and values[index]
-		    var y1 = (index == 0) ? values[0] : values[index-1];
-		    var y2 = values[index];
-		    var y = y1;
-		    if (graph_x != x1) y += (graph_x - x1)*(y2 - y1)/(x2 - x1);
-
-		    // annotate plot with value of signal at marker
-		    c.fillStyle = element_style;
-		    c.fillText('\u2588\u2588\u2588\u2588\u2588',tx-3,ty);
-		    c.fillStyle = probe_colors_rgb[graph.y_values[plot][0]];
-		    c.fillText(engineering_notation(y,3,false),tx,ty);
-		    ty += 14;
+		if (x2 != undefined) {
+		    // for each plot, interpolate and output value at intersection with marker
+		    c.textAlign = 'left';
+		    var tx = graph.left_margin + 4;
+		    var ty = graph.top_margin;
+		    for (var plot = 0; plot < graph.y_values.length; plot++) {
+			var values = graph.y_values[plot][1];
+
+			// interpolate signal value at graph_x using values[index-1] and values[index]
+			var y1 = (index == 0) ? values[0] : values[index-1];
+			var y2 = values[index];
+			var y = y1;
+			if (graph_x != x1) y += (graph_x - x1)*(y2 - y1)/(x2 - x1);
+
+			// annotate plot with value of signal at marker
+			c.fillStyle = element_style;
+			c.fillText('\u2588\u2588\u2588\u2588\u2588',tx-3,ty);
+			c.fillStyle = probe_colors_rgb[graph.y_values[plot][0]];
+			c.fillText(engineering_notation(y,3,false),tx,ty);
+			ty += 14;
+		    }
 		}
 	    }
 	}
@@ -3086,7 +3110,8 @@ schematic = (function() {
 	    this.add_connection(0,0);   // +
 	    this.add_connection(0,16);  // -
 	    this.add_connection(48,8);  // output
-	    this.bounding_box = [0,-8,48,24];
+	    this.add_connection(24,32);  // ground
+	    this.bounding_box = [0,-8,48,32];
 	    this.update_coords();
 	}
 	OpAmp.prototype = new Component();
@@ -3104,7 +3129,9 @@ schematic = (function() {
 	    // inputs and output
 	    this.draw_line(c,0,0,8,0);
 	    this.draw_line(c,0,16,8,16);
+	    this.draw_text(c,'gnd',37,18,property_size);
 	    this.draw_line(c,40,8,48,8);
+	    this.draw_line(c,24,16,24,32);
 	    // + and -
 	    this.draw_line(c,10,0,16,0);
 	    this.draw_line(c,13,-3,13,3);
@@ -3176,6 +3203,9 @@ schematic = (function() {
 	source_functions = {
 	    'dc': ['DC value'],
 
+	    'impulse': ['Height',
+			'Width (secs)'],
+
 	    'step': ['Initial value',
 		     'Plateau value',
 		     'Delay until step (secs)',