14-12-2023: Design of drive capability

Lecture: EE4109-10

Location Pulse Hall 4

Time: 08:45 - 15:30

Design considerations drive capability

1. Together, the current and voltage drive requirements determine the with, the length, and the quiescent operating conditions of the controllers’ output stage transistors.

2. In a top down approach we assign budgets to contributions to the voltage and current drive requirements of the controller.

3. In most cases the mimimum supply voltage is an application requirement and the controller needs to be able to drive the load and the feedback network at this lowest supply voltage.

4. The difference between the peak-peak supply voltage and the peak-peak controller output voltage is called the voltage headroom. Together, all DC bias voltage errors and DC saturation voltages of the output stage devices should maximally add up to this voltage headroom.

5. The current drive capability of the controller is determined by the sum of the load current, the current through the feedback network, and the output stage’s bias current errors.

6. Since biasing errors affect the controller drive requirements, an adequate biasing methed, capable of keeping the biasing errors at the amplifier ports within specified budgets, must be designed before designing the controller.

Group exersise (Hearing loop receive amplifier)

1. Continue with the exercise from the previous lecture.

2. Specify the voltage and current drive requirements of the controller for the case in which the contribution of the feedback network to the variance of the output voltage can be 20% of the total budget.

3. Set-up a biasing scheme for the amplifier that maximizes its voltage drive capability. You can think of application of

   • Negative feedback biasing

   • Compensation or model-based feedback techniques

   • Auto-zero techniques

4. If the voltage and current drive capability of a CS stage is a performance requirement, what would you specify as a useful cost factor for it.