ZigBee PRO Communication Controller Chip


The GP490 controller chip

The GP490 is an ultra-low-power ZigBee PRO communication controller. It supports the ZigBee PRO chip features, including bidirectional commissioning, bidirectional communication, and full security mode.

The controller is specifically designed for low-power smart home applications including door, window, and temperature sensors and light switches. Equipped with the energy-optimized GP490, these low-power, low-data rate smart home applications can operate on a coin cell battery for more than 10 years.

The GP490 development kit with reference design and software can help device manufacturers build low-cost, low-power sensor nodes, optimized for standard battery and coin-cell battery operation. Guidelines and tools are provided to ensure an efficient ZigBee certification for a cost-optimized feature set of the ZigBee Home Automation (HA 1.2) Application Profile.

The low-cost GP490 enables developers and manufacturers to supply ZigBee Smart Home sensor solutions starting at $5 each. Contact GreenPeak Technologies for specific pricing.

GreenPeak Technologies

Compact Wi-Fi Transceiver


The LEMOS-LMX-WiFi wireless transceiver

The LEMOS-LMX-WiFi is a compact wireless transceiver that can operate on IEEE 802.11 networks. It is supported by a 32-bit microcontroller running a scalable TCP/IP stack. The transceiver is well suited for wireless embedded applications involving digital remote control, digital and analog remote monitoring, asset tracking, security systems, point of sale terminals, sensor monitoring, machine-to-machine (M2M) communication, environmental monitoring and control.

The 40.64-mm × 73.66-mm transceiver is available in two models: integrated PCB antenna or external antenna. Its features include software-selectable analog and digital I/O pins, a 2-Mbps maximum data rate, and a unique IEEE MAC address.

The LEMOS-LMX-WiFi can be powered by any 3.3-V to – 6-VDC source that can deliver 200 mA of current. The transceiver can interface to external devices that communicate via USART, I2C, and SPI. It also supports infrastructure and ad hoc networks.

Contact Lemos International for pricing.

Lemos International, Inc.

John Safrit Wins the CC Code Challenge (Week 24)

We have a winner of last week’s CC Weekly Code Challenge, sponsored by IAR Systems! We posted a code snippet with an error and challenged the engineering community to find the mistake!

Congratulations to John Safrit of Mebane, North Carolina, United States  for winning the CC Weekly Code Challenge for Week 24! John will receive a CC T-shirt and a one-year subscription to Circuit Cellar.

John’s correct answer was randomly selected from the pool of responses that correctly identified an error in the code. John answered:

Line#22: need to terminate space string, add: space[d]=’';


You can see the complete list of weekly winners and code challenges here.

What is the CC Weekly Code Challenge?
Each week, Circuit Cellar’s technical editors purposely insert an error in a snippet of code. It could be a semantic error, a syntax error, a design error, a spelling error, or another bug the editors slip in. You are challenged to find the error.Once the submission deadline passes, Circuit Cellar will randomly select one winner from the group of respondents who submit the correct answer.

Inspired? Want to try this week’s challenge? Get started!

Submission Deadline: The deadline for each week’s challenge is Sunday, 12 PM EST. Refer to the Rules, Terms & Conditions for information about eligibility and prizes.

Issue 280: EQ Answers

What is the key difference between the following two C functions?

#define VOLTS_FULL_SCALE 5.000
#define KPA_PER_VOLT 100.0
#define KPA_THRESHOLD 200.0

/* adc_reading is a value between 0 and 1
bool test_pressure (float adc_reading)
  float voltage = adc_reading * VOLTS_FULL_SCALE;
  float pressure = voltage * KPA_PER_VOLT;

  return pressure > KPA_THRESHOLD;

bool test_pressure2 (float adc_reading)
  float voltage_threshold = KPA_THRESHOLD / KPA_PER_VOLT;
  float adc_threshold = voltage_threshold / VOLTS_FULL_SCALE;

  return adc_reading > adc_threshold;

The first function, test_pressure(), converts the ADC reading to engineering units before making the threshold comparison. This is a direct, obvious way to implement such a function.

The second function, test_pressure2(), converts the threshold value to an equivalent ADC reading, so that the two can be compared directly.

The key difference is in performance. The first function requires that arithmetic be done on each reading before making the comparison. However, the calculations in the second function can all be performed at compile time, which means that the only run-time operation is the comparison itself.

How many NAND gates would it take to implement the following translation table? There are five inputs and eight outputs. You may consider an inverter to be a one-input NAND gate.

Inputs Outputs
A B C D E   F G H I J K L M
1 1 1 1 1 0 0 0 0 1 1 1 1
0 1 1 1 1 0 0 0 0 0 0 1 1
0 0 1 1 1 0 0 0 0 0 0 0 0
0 0 0 1 1 1 0 0 0 0 0 1 1
0 0 0 0 1 1 0 0 0 1 1 1 1


First of all, note that there are really only four inputs and three unique outputs for this function, since input E is always 1 and outputs GHI are always 0. The only real outputs are F, plus the groups JK and LM.

Since the other 27 input combinations haven’t been specified, we can take the output values associated with all of them as “don’t care.”

The output F is simply the inversion of input C.

The output JK is high only when A is high or D is low.

The output LM is high except when B is low and C is high.

Therefore, the entire function can be realized with a total of five gates:


Quick history quiz: Who were the three companies who collaborated to create the initial standard for the Ethernet LAN?

The original 10-Mbps Ethernet standard was jointly developed by Digital Equipment Corp. (DEC), Intel, and Xerox. It was released in November 1980, and was commonly referred to as “DIX Ethernet.”

What was the name of the wireless network protocol on which Ethernet was based? Where was it developed?

The multiple access with collision detection protocol that Ethernet uses was based on a radio protocol developed at the University of Hawaii. It was known as the “ALOHA protocol.”

A Look at Low-Noise Amplifiers

Maurizio Di Paolo Emilio, who has a PhD in Physics, is an Italian telecommunications engineer who works mainly as a software developer with a focus on data acquisition systems. Emilio has authored articles about electronic designs, data acquisition systems, power supplies, and photovoltaic systems. In this article, he provides an overview of what is generally available in low-noise amplifiers (LNAs) and some of the applications.

By Maurizio Di Paolo Emilio
An LNA, or preamplifier, is an electronic amplifier used to amplify sometimes very weak signals. To minimize signal power loss, it is usually located close to the signal source (antenna or sensor). An LNA is ideal for many applications including low-temperature measurements, optical detection, and audio engineering. This article presents LNA systems and ICs.

Signal amplifiers are electronic devices that can amplify a relatively small signal from a sensor (e.g., temperature sensors and magnetic-field sensors). The parameters that describe an amplifier’s quality are:

  • Gain: The ratio between output and input power or amplitude, usually measured in decibels
  • Bandwidth: The range of frequencies in which the amplifier works correctly
  • Noise: The noise level introduced in the amplification process
  • Slew rate: The maximum rate of voltage change per unit of time
  • Overshoot: The tendency of the output to swing beyond its final value before settling down

Feedback amplifiers combine the output and input so a negative feedback opposes the original signal (see Figure 1). Feedback in amplifiers provides better performance. In particular, it increases amplification stability, reduces distortion, and increases the amplifier’s bandwidth.

 Figure 1: A feedback amplifier model is shown here.

Figure 1: A feedback amplifier model is shown.

A preamplifier amplifies an analog signal, generally in the stage that precedes a higher-power amplifier.

Op-amps are widely used as AC amplifiers. Linear Technology’s LT1028 or LT1128 and Analog Devices’s ADA4898 or AD8597 are especially suitable ultra-low-noise amplifiers. The LT1128 is an ultra-low-noise, high-speed op-amp. Its main characteristics are:

  • Noise voltage: 0.85 nV/√Hz at 1 kHz
  • Bandwidth: 13 MHz
  • Slew rate: 5 V/µs
  • Offset voltage: 40 µV

Both the Linear Technology and Analog Devices amplifiers have voltage noise density at 1 kHz at around 1 nV/√Hz  and also offer excellent DC precision. Texas Instruments (TI)  offers some very low-noise amplifiers. They include the OPA211, which has 1.1 nV/√Hz  noise density at a  3.6 mA from 5 V supply current and the LME49990, which has very low distortion. Maxim Integrated offers the MAX9632 with noise below 1nV/√Hz.

The op-amp can be realized with a bipolar junction transistor (BJT), as in the case of the LT1128, or a MOSFET, which works at higher frequencies and with a higher input impedance and a lower energy consumption. The differential structure is used in applications where it is necessary to eliminate the undesired common components to the two inputs. Because of this, low-frequency and DC common-mode signals (e.g., thermal drift) are eliminated at the output. A differential gain can be defined as (Ad = A2 – A1) and a common-mode gain can be defined as (Ac = A1 + A2 = 2).

An important parameter is the common-mode rejection ratio (CMRR), which is the ratio of common-mode gain to the differential-mode gain. This parameter is used to measure the  differential amplifier’s performance.

Figure 2: The design of a simple preamplifier is shown. Its main components are the Linear Technology LT112 and the Interfet IF3602 junction field-effect transistor (JFET).

Figure 2: The design of a simple preamplifier is shown. Its main components are the Linear Technology LT1128 and the Interfet IF3602 junction field-effect transistor (JFET).

Figure 2 shows a simple preamplifier’s design with 0.8 nV/√Hz at 1 kHz background noise. Its main components are the LT1128 and the Interfet IF3602 junction field-effect transistor (JFET).  The IF3602 is a dual N-channel JFET used as stage for the op-amp’s input. Figure 3 shows the gain and Figure 4 shows the noise response.

Figure 3: The gain of a low-noise preamplifier.

Figure 3: The is a low-noise preamplifier’s gain.


Figure 4: The noise response of a low-noise preamplifier

Figure 4: A low-noise preamplifier’s noise response is shown.

The Stanford Research Systems SR560 low-noise voltage preamplifier has a differential front end with 4nV/√Hz input noise and a 100-MΩ input impedance (see Photo 1a). Input offset nulling is accomplished by a front-panel potentiometer, which is accessible with a small screwdriver. In addition to the signal inputs, a rear-panel TTL blanking input enables you to quickly turn the instrument’s gain on and off (see Photo 1b).

Photo 1a:The Stanford Research Systems SR560 low-noise voltage preamplifier

Photo 1a: The Stanford Research Systems SR560 low-noise voltage preamplifier. (Photo courtesy of Stanford Research Systems)

Photo 1 b: A rear-panel TTL blanking input enables you to quickly turn the Stanford Research Systems SR560 gain on and off.

Photo 1b: A rear-panel TTL blanking input enables you to quickly turn the Stanford Research Systems SR560 gain on and off. (Photo courtesy of Stanford Research Systems)

The Picotest J2180A low-noise preamplifier provides a fixed 20-dB gain while converting a 1-MΩ input impedance to a 50-Ω output impedance and 0.1-Hz to 100-MHz bandwidth (see Photo 2). The preamplifier is used to improve the sensitivity of oscilloscopes, network analyzers, and spectrum analyzers while reducing the effective noise floor and spurious response.

Photo 2: The Picotest J2180A low-noise preamplifier is shown.

Photo 2: The Picotest J2180A low-noise preamplifier is shown. (Photo courtesy of picotest.com)

Signal Recovery’s Model 5113 is among the best low-noise preamplifier systems. Its principal characteristics are:

  • Single-ended or differential input modes
  • DC to 1-MHz frequency response
  • Optional low-pass, band-pass, or high-pass signal channel filtering
  • Sleep mode to eliminate digital noise
  • Optically isolated RS-232 control interface
  • Battery or line power

The 5113 (see Photo 3 and Figure 5) is used in applications as diverse as radio astronomy, audiometry, test and measurement, process control, and general-purpose signal amplification. It’s also ideally suited to work with a range of lock-in amplifiers.

Photo 3: This is the Signal Recovery Model 5113 low-noise pre-amplifier.

Photo 3: This is the Signal Recovery Model 5113 low-noise preamplifier. (Photo courtesy of Signal Recovery)

Figure 5: Noise contour figures are shown for the Signal Recovery Model 5113.

Figure 5: Noise contour figures are shown for the Signal Recovery Model 5113.

This article briefly introduced low-noise amplifiers, in particular IC system designs utilized in simple or more complex systems such as the Signal Recovery Model 5113, which is a classic amplifier able to obtain different frequency bands with relative gain. A similar device is the SR560, which is a high-performance, low-noise preamplifier that is ideal for a wide variety of applications including low-temperature measurements, optical detection, and audio engineering.

Moreover, the Krohn-Hite custom Models 7000 and 7008 low-noise differential preamplifiers provide a high gain amplification to 1 MHz with an AC output derived from a very-low-noise FET instrumentation amplifier.

One common LNA amplifier is a satellite communications system. The ground station receiving antenna will connect to an LNA, which is needed because the received signal is weak. The received signal is usually a little above background noise. Satellites have limited power, so they use low-power transmitters.

Telecommunications engineer Maurizio Di Paolo Emilio was born in Pescara, Italy. Working mainly as a software developer with a focus on data acquisition systems, he helped design the thermal compensation system (TCS) for the optical system used in the Virgo Experiment (an experiment for detecting gravitational waves). Maurizio currently collaborates with researchers at the University of L’Aquila on X-ray technology. He also develops data acquisition hardware and software for industrial applications and manages technical training courses. To learn more about Maurizio and his expertise, read his essay on “The Future of Data Acquisition Technology.”