Circuit Simulation Some humbling thoughts…

1. Circuit SimulationSome humbling thoughts… Manfred Wendt Fermilab

2. Circuit Simulation: For What? Typical beam instrument, e.g. BPM, toroid, WCM, PMT, etc. Beam Pickup Detector Analog Signal Processing A D C Digital Signal Processing DAQ & LAN Interface Clock & Trigger Distribution Analog Domain Digital Domain Manfred Wendt, Fermilab/AD-Instrumentation

3. Circuit Simulation Domains • Digital signal simulation is mostly based on vendor supplied simulators (e.g. Quartex II, etc.). • No model data is available for most complex semiconductors (ADC, DAC, T&H amps, limiters, many – if not most - analog parts). • Circuit simulation may still be useful for critical sections and subsystems: • Gain stages • Passive sections (filters, diplexers, hybrids, transmission-lines) • RF- & microwave circuits • Layout effects, cross-talk, reflections • Noise and temperature analysis • Pickup detectors (button, stripline, cavity & other monitors • High-speed digital I/O (CLK distribution, PECL & LVDL circuits, single-ended to differential transition) Manfred Wendt, Fermilab/AD-Instrumentation

4. Circuit Simulator Software • “Brainware” • Pencil and paper • Apply Kirchhoff and Ohm’s law for a simple, idealized subcircuit. • Analytic result! Limited to linear circuits. • Freeware • Berkley SPICE and variants (google “free spice simulator”). • Student versions, often limited. • Simulators for special purposes. • $$$ware • Schematic entry • Combined with layout system, or add-on to layout system. • Design suites, including various circuit and EM simulators. Manfred Wendt, Fermilab/AD-Instrumentation

5. Capabilities and Characteristics • Circuit simulators can • Fully analyze the circuit (based on the models). • Have sometimes (often limited) synthesis capabilities. • Numerical solution of the circuit topology • Circuit elements • Lumped elements based on ideal models • Distributed elements based on analytic solutions or approximations of the EM problem • Nonlinearities, noise & temperature and other effects may be included in some models • User specified (analytical) models and sources. Manfred Wendt, Fermilab/AD-Instrumentation

6. Circuit Simulator Types • Linear Solvers: • DC, AC, S-parameter, etc. • Frequency domain solution in steady state • Nonlinear Solvers (e.g. Harmonic Balance): • Small signal analysis around the working point. • Spectral, distortion and other characterization of the frequency harmonics. • Transient Solvers (e.g. SPICE): • Approximate solution of the system of differential equations • Time domain approach includes all transient effects and initial values. • Special Solvers: • Analytic circuit analysis, EM solvers, circuit synthesis, etc. Manfred Wendt, Fermilab/AD-Instrumentation

7. Simulation Examples Fermilab Main Injector BPM Upgrade Project Manfred Wendt, Fermilab/AD-Instrumentation

8. Simulation Examples (cont.) MI BPM Analog Signal Processing 2. 3. • Entire input section • Absorptive low-pass • Diplexer Manfred Wendt, Fermilab/AD-Instrumentation

9. Simulation Examples (cont.) MI BPM Analog Circuit (1 ch., 2.5 & 53 MHz) Manfred Wendt, Fermilab/AD-Instrumentation