Electronic Design published my
first Idea for Design, “AC-DC
Converter Runs Off One Power
Supply” (April 16, 1992, p.
93), more than 16 years ago
(Fig. 1). It set a theme that I
have continued to employ ever
since—using the nifty venue of
IFDs to present and develop new circuit design ideas
and themes to the engineering community. Over the
years, examples of some of those basic concepts and
the IFDs that showcased them (which are still available
at www.electronicdesign.com) still stand out.
Take Back Half
High-performance temperature control looks easy
enough in theory, but is far from simple in practice.
The Take Back Half (TBH) method takes deliberate
advantage of the (approximate) equality of straightintegration’s
undamped over/undershoots
(Fig. 2).
Experience gained from applying TBH reveals that
the algorithm’s stability is robust. Simulation and
experimentation agree that convergence can always
be achieved while steady-state error remains equal to
zero. Four of my IFDs use TBH:
• “Take Back Half: A Novel Integrating Temperature-
Control Algorithm,” Dec. 4, 2000, p. 132-134, ED
Online 4994
• “Precision Thermostat Uses TBH and AC Feed-
Forward Compensation,” March 19, 2001, p.
126-128, ED Online 4129
• “‘Take-Back-Half’ HVAC Thermostat Is Precise
and Energy Efficient,” July 9, 2001, p. 100-102,
ED Online 3850
• “Thermostat for High-Altitude Atmospheric
Sampler is Fault-Tolerant,” Nov. 19, 2001, p.
88-90, ED Online 3523
Thermal Anemometry
Among the techniques for measuring airspeed,
thermal anemometry has the virtues of simplicity
and easy miniaturization
(Fig. 3). Thermal airspeed
sensors face two practical problems, though. First,
the accuracy of the thermal airspeed measurement
depends on accurate compensation for ambient temperature,
and accurate temperature measurement isn’t
easy, so portable operation is problematic. Next, the
second-order exponent makes the raw sensor output
nonlinear with airspeed. So, thermal anemometers
typically need some provision for measurement linearization.
Five of my IFDs look at these problems:
• “Portable Airspeed Measurement,” Jan. 22, 1996,
92-94, ED Online 19696
• “Linear Pitot-Tube Air-Speed Indicator,” June 9,
1997, p. 164-166, ED Online 6396
• “Low Power Thermal Airspeed Sensor,” May 25,
1998, p. 116-118, ED Online 6292
• “Low-Power Solid-State Airflow Detector,”
Jan. 22, 2001, p. 118-125, ED Online 4294
• “Series-Connected Transistors Use
Differential Heating to Sense Airflow,” May
7, 2001, p. 99-100, ED Online 3990
Self-Compensating Charge Pump
The classic diode-capacitor charge pump is
one of the many starting points for voltageto-
frequency converter designs (Fig. 4). An
obvious snag with this scheme is the need
to cope with the forward voltage drop of VD
of the pump diodes, including the associated
temperature dependence. But commonly used
methods for doing so sometimes run into trouble
caused by parasitic capacitiance. Two IFDs
illustrate a different VD fix, in which multiple
diodes work together to make a compensatory
charge pulse. Not only do we get compensation
for the bothersome VDs, but the effects of
stray capacitance also get rubbed out.
• “Nanopower VFC Includes Self-
Compensating Charge Pump,” June 22,
1998, p. 131, ED Online 6283
• “Available-Light Phototachometer Simplifies
Outdoor Remote Sensing,” Jan. 25, 1999, p.
96-97, ED Online 6237