Static (DC)
 Dynamic (AC)
Linear
 Error
Source
 Offset Voltage
DC Bias Current
Finite Bandwidth
GHLM Text
 Sec. 6.2.1, 6.2.2, 6.2.3
 Sec. 9.2
Analysis
Strategy
  1. Add DC sources to ideal op-amp to model errors

  2. Analyze with superposition to find contribution of each error source to output voltage

  3. Add in "worst case" fashion
  • Offset voltage can be either polarity

  • Bias current polarity known from type of op-amp input stage
 Model closed loop behavior with first-order transfer function:
  • DC gain from ideal op-amp assumptions

  • Closed loop 3dB frequency fBCL from gain-bandwdith product relationship
Gain-bandwidth product procedure:
  1. Redraw circuit with all inputs suppressed (set = 0)

  2. Find feedback factor β (fraction of output fed back to inverting input)

  3. Closed loop bandwidth fBCL will be unity gain frequency ft mutliplied by β
Non-Linear
 Error
Source
 Output voltage swing limit
Output current limit
 Slew rate limit
GHLM Text
 Sec. 5.4.6
 Sec. 9.6
Analysis
Strategy
  1. Determine maximum total vOUT, iOUT, excursion at op-amp output from linear system model

  2. Compare maximum, minimum to op-amp limits
  1. Determine vOUT(t) from linear system behavior (transfer function for sine wave, general exponential response for step)

  2. Calculate time derivative dvOUT(t)/dt

  3. Compare maximum, minimum dvOUT(t)/dt to op-amp slew rate limit