Current mirrors are common circuits but are mostly invisible, except to designers of analog or mixed-signal integrated circuits who can use large numbers of current mirrors on a single chip. A current mirror copies a current through one active device (such as a BJT or MOSFET) by controlling the current in another active device. If […]
Analog ICs
What can you make with MEMS technology?
Microelectromechanical systems (MEMS) has several names, including micro-electro-mechanical systems, and micromechatronic systems. In Japan, MEMS is called micromachines, while in Europe, it’s referred to as microsystem technology (MST). Whatever name that’s used, MEMS devices are made using components measuring from 1 to 100 μm (0.001 to 0.1 mm), with MEMS devices ranging from 20 μm […]
Common-mode filters boast 10.7 GHz bandwidth
New common-mode filters from STMicroelectronics have an extremely wide differential bandwidth of 10.7GHz to protect antenna sensitivity in adjacent wireless circuitry from the latest serial digital interfaces. The 2-channel ECMF2-40A100N10 and 4-channel ECMF4-40A100N10 are compatible with high-speed interface standards including USB 3.2 Gen 2, USB4, HDMI 2.1, and DisplayPort. With their low serial resistance of just 3Ω, which […]
What’s the difference between equalizers?
Equalizers are used to alter the performance of signal chains. In some cases, that means linearizing signal chain performance. In other cases, equalizers are used to introduce nonlinearities. As a result, equalizer designs vary widely from simple passive circuits to complex multi-stage designs and active circuits. This FAQ reviews equalizer basics, looks at equalizers for […]
What do you do with a bucket brigade device?
A bucket brigade device (BBD) is a discrete-time analog delay line using capacitors that has been replaced in most digital signal processing applications. But it continues to be used in some specialty applications such as guitar and audio sound effects and some types of sensors. It consists of a series of capacitance sections where a […]
What’s a logarithmic resistor ladder good for?
A logarithmic resistor ladder consists of a resistor string and switches designed to attenuate a signal. The state of the switches can be considered to represent a digital code proportional to the logarithm of the attenuation ratio. Logarithmic attenuation is useful when a large dynamic range is needed. Audio volume control and fading/balancing audio signals […]
What causes noise in analog designs and how can it be controlled?
Controlling noise in analog and mixed-signal circuits is important but not simple. Data integrity is dependent on controlling noise in the signal chain. If left uncontrolled, noise can impair or disrupt system operation. This FAQ starts by looking at the various sources and types of noise, looks at how noise can enter the signal chain […]
Five considerations for mixed-signal PCB layouts
Printed circuit board (PCB) layout is an important activity when developing mixed-signal applications. A lot can go wrong, and everything needs to be correct for a successful design. Impedance control is an obvious consideration, but it needs to include trace resistance as well as parasitic inductances and capacitances. Maintaining signal integrity can be challenging. This […]
When is a high CMRR needed in an op amp?
Common mode rejection ratio (CMRR), also called common mode rejection (CMR), quantifies the ability of an operational amplifier (op amp) to reject common-mode signals. Common-mode signals are signals that appear simultaneously and in phase on both inputs. This FAQ begins by defining what CMRR is and how it’s quantified, reviews some design considerations related to […]
What are reflectionless filters, Part 3: Basic principles
Standard filters reflect unwanted stopband energy, but reflectionless filters present a seamless impedance across both stopband and passband, which greatly improves performance of the RF signal chain. Beginning in 2011, Dr. Matthew A. Morgan of the National Radio Astronomy Observatory (NRAO) in Charlottesville, West Virginia, working with Tod A. Boyd and later with Wavley M. […]
