Examples of Typical Analog Circuit Design Engagements
This section describes some typical projects that we have been involved with in the past. The examples include the background, what was done to assist the project and the results.
Sample Analog Projects
Design Review and Analysis of a Hot Insertion Circuit
Analog Design Interface for High Speed PCB
Design of a High Performance, Low Noise Amplifier Circuit
Design of a Special Purpose Driver Circuit
Design of a Low Power, Battery Operated Analog Circuit
Design Review and Analysis of a Hot Insertion Circuit
Situation
The Client was Designing a Hot Board Insertion circuit and was concerned about the ability of the Power Supply to sustain the “current spike” presented by this new circuit design. They needed the engineering capacity to create the appropriate Spice Simulation models and verify them in the actual system.
Tasks Performed
I created a model for the hot insertion portion of the circuit that included a MOSFET and its associated components. I then ran simulations and tests in the Lab to verify how well the models performed in relation to the actual circuitry. I then updated the model until it validated what was measured in the system.
Results
The Client was more confident that the new design would function adequately in mass production without manufacturing test and field failures. In production, the final circuit worked well.
Analog Design Interface for High Speed PCB
Situation
The Client wanted a design review of a high-speed PCB design layout to ensure that the high-speed signals would allow the various ICs to communicate with each other both between and internally to the boards.
Tasks Performed
I worked with the Client to identify the critical signals on the schematics. Assistance was given to select the appropriate PC Board material. Layout rules were generated for the layout person to follow. I interfaced with the layout person to answer questions during layout and check progress.
Performed checks of critical lines after the layout was complete to ensure that layout rules were followed correctly.
After the board was fabricated, tests were run to ensure the critical lines had the correct impedance. Measurements were made on the Assembled board to ensure signal integrity was maintained.
Results
When circuit functionality was tested, there were very few problem areas related to the layout on the board. The analysis prevented the need for a massive new layout that would have seriously extended the schedule.
Design of a High Performance, Low Noise Amplifier Circuit
Situation
The client had insufficient knowledge of analog electronics to create a special amplifier for very low level, wide bandwidth signals for a high performance photodiode amplifier to feed a high speed analog to digital converter.
Tasks Performed
I worked with the client to identify the specifications required for the new circuit. Then, I created a model and block diagram for the circuit architecture and did initial simulations for estimated requirements.
I searched through available operational amplifiers and their characteristics to come up with suitable candidates for the design. Then, I captured the schematic, indicating critical signal lines on the schematic for layout person. I also created a formal Spice model of the circuit and simulated it before it was fabricated. Then, I reviewed layout before fabrication. Finally, I tested the circuit after the PCB was fabbed and assembled. This included validation of Spice Model simulation.
Results
A design was created that met the circuit specifications and that permitted the design to be available in rapid time.
Design of a Special Purpose Driver Circuit
Situation
The client was doing a redesign of an existing PCB design to expand the capabilities of a circuit, and at the same time shrink its size. They wanted the circuit to be simple, and not to utilize a microcontroller. This would keep development costs low. The circuit was to take in a standard interface, and drive a number of digital outputs using a standard Windows program as a driver.
Tasks Performed
I created a specification and a plan to develop the PCB. This included a block diagram and an initial selection of critical components. Then, I captured the schematic of the circuit. Then, I worked with the layout person to get the PCB layed out properly, and then I checked results before fab. After this, I interfaced with Fab and assembly houses to make the initial PCBs.
After Fab and Assembly, I tested the PCBs and made them functional. Then I completed the documentation for the entire design, and worked with client to make it ready for production. During this process, I held the necessary Design and Status Reviews throughout the project.
Results
A PCB that met all of the circuit specifications, and that permitted the client to test a new approach to the system design in record time. The design was largely ready for production, once proof of concept was assured.
Design of a Low Power, Battery Operated Analog Circuit
Situation
The client was creating a proof of concept model for a mixed signal, battery powered very low power circuit. The circuit received information via a photocell, that was encoded in the video of a TV Raster.
Tasks Performed
I created a specification and a plan to develop the circuit. The spec included a block diagram and selection of low power circuit techniques and components. I designed and captured the schematic of the circuit. Then, I interfaced with the layout person to create a PCB model of the circuit. After this, I led and interfaced with the fabrication and assembly of the circuit board.
I tested PCBs and made them functional. Then, I documented the entire design and worked with the Client to prepare it for incorporation into the mixed signal ASIC. I held the necessary Design and Status Reviews throughout the project.
Results
A circuit that met all of the circuit specifications was created, permitting the Client to test the system design in record time. Once the proof of concept was validated, the design was incorporated into an ASIC.