ADI Constant Current Bias Solution
Power amplifier PA is an important device in communication systems. In order for the PA to operate at the proper bias and maximize its performance, its bias control circuitry cannot be ignored. From the perspective of bias, PA can be divided into two categories, one is a self-bias amplifier and the other is an external bias amplifier. The self-biased amplifier has an internal circuit for the socially appropriate bias point of operation. These amplifiers are typically suitable for broadband low-power applications and are simple to use. However, it may not provide the best performance because the internal resistive paranoid circuit does not adequately compensate for differences in batch, device, and temperature. For biasing the external bias amplifier is mainly composed of a constant gate voltage and a constant drain current. Constant drain current is used in many scenarios. This method first sets the gate voltage to achieve the desired drain current value, then monitors the amplifier's drain current and continuously adjusts the gate voltage to keep the drain current constant. This article focuses on the ADI constant current biasing solution. The main characteristics of these active bias controllers can be seen from the above table. They can generate the commonly required gate voltage negative voltage and the second stage gate voltage. At the same time, they can provide overcurrent and undercurrent alarms, and the threshold can be set. . Since the main principles are the same, the following focuses on the use of the active bias controller with the HMC980. The figure above shows a typical application diagram of the HMC980 active bias controller, and the structure is simple and clear. The target drain current of the PA is set by the resistance of Pin20. In order to obtain a stable bias current, R10 requires the use of high-precision and low-temperature resistance components. Since the switch tube inside the HMC 980 itself has an impedance, Vdd can add the voltage consumed on the switch tube according to the drain voltage required by the latter stage PA. VGATE provides the appropriate voltage for the PA, and VNEG is used to set the voltage range of the VGATE. The default is -2.46V. The voltages of the VNEG and VGATE pins can be adjusted by connecting the resistor values ​​on VNEGFB and VGATEFB. The CPOUT pin needs to be connected to VNEG through two diodes and a capacitor to form a negative voltage generating circuit. At the same time, P21, 22, 23 can set the overcurrent and undercurrent alarm threshold by configuring the resistor. The capacitor on the VGATE can be used as a filtering effect on the one hand to adjust the gate voltage rise time. A small resistor can also be connected in series to this pin when needed to avoid oscillations caused by overshoot caused by voltage changes. In addition to the above three chips, ADI also has a single-chip AD7293 with integrated ADC, DAC, current sensing and temperature sensor. Its structure is as follows. Its current detection supports common mode voltages up to 60V. The output voltage range of the DAC can be set to -5~0V, -4V~1V and 0V~5V. It can meet the biasing needs of almost all common PAs. This article briefly introduces ADI's two active bias control ICs for constant drain current amplifiers, an analog closed-loop approach represented by the HMC 980-bit, which is simple and flexible to use. However, its supported drain voltage and drain current are limited in size. The other is a monolithic integrated current sense, temperature sensor and ADC, DAC AD7293. It supports a large number of channels and a wide range of drain voltage and drain current.
Toggle switches
Toggle switches, also called On Off Toggle Switches, is often used as the switching device of the equipment stalls. Meanwhile, we are also offer our customers Key Switches, Metal Switches, Automotive Switches, Push Button Switches, etc.
The Electrical Toggle Switches is a manually controlled Toggle Switches similar to the dial switch. Most of this Latching Toggle Switches are widely used in on-off control of AC and DC power circuits, and are less commonly used in circuits of several kilohertz or up to 1 megahertz. Let's take a look at the following.
1. Splash-proof knob button switch
The panel is installed with a splash-proof `O` ring seal, and the knob is a ball. It is a splash-proof ball button knob switch. Its terminals are in a straight line and the bottom of the terminals is sealed with epoxy resin. Strong corrosion resistance, suitable for automotive parts
2. Vertical Mount Right Angle Toggle Switch
The vertical mounting of the terminals and the terminal pins are right-angled, so it is a vertically mounted right-angled toggle switch. Its contacts are gold-plated and highly reliable. Mostly used in anti-theft devices, alert system.
3. Bipolar single toggle switch
At the same time, the switch breaks the phase line and the N line and controls one branch. Therefore, it is a bipolar single toggle switches. The contacts are in 3PDT form and are used for multimedia speakers and stereos.
4. Standard surface mount unthreaded toggle switches
The terminal adopts the standard mounting mode. Its sleeve has no thread. It is called a standard surface mount screw-less switch. The contacts are SPDT and its electrical life is as high as 55,000. Used for medical equipment
5. Horizontally mounted right-angle toggle switch
Compared to the vertical switch, it only changes direction to horizontal, so it is horizontally mounted right-angle toggle switch. The contacts are double-pole double-throw and the bottom of the terminal is Epoxy Seal. Mostly used for computer peripherals.
Toggle Switches,Toggle Switch On Off,Toggle Switch Autozone,Toggle Switch Home Depot YESWITCH ELECTRONICS CO., LTD. , https://www.yeswitches.com
