What is negative voltage? Respecting voltage, everything is opposite. Different conductance has different potential between body. It is OK that this means a voltage prep above another voltage. This kind of circumstance falls to won’t use “ negaive electricity to press the description of ” commonly. The negative tension that we say is to point to a report to press the ground potential under the system. Graph 1 it is voltage of power source of a 3.3V and 0V system the give typical examples of ground potential. In this system, need is measured and record the signal of sensor. These signal may be in + between 2.5V and –2.5V.

 

To detect these signal, we are used + the operation amplifier of the voltage of negaive electricity source of the voltage of positive electricity source of 3.3V and –3.3V. And had offerred in the system + 3.3V positive electricity is pressed. The –3.3V that needs to place loses voltage, the –5V that can use a system will arise. This voltage course may come from the power source that is based on transformer, normally this voltage adjusts accurately without the course. Generate –3.3V definitely for essence of life, we need to use linear manostat.

 

Have on the market numerous the linear manostat that applies to positive electricity pressing can offer an alternative. In the application that changes negative voltage in need, whether can you use this to plant linear manostat?

 

Graph 1 showed those who be used in this kind of application linear manostat. Those who pursue medium is adjustable the adjustment that resistor represents linear manostat component. Linear to this kind manostat for IC, the voltage relation between VIN, VOUT and GND connector is identical, in resembling pressing application in positive electricity same. However, use in this kind of environment linear manostat has a few drawback. This circuit comes to use resistor voltage divider adjust the output voltage that is based on –5V voltage course, is not to be based on 0V voltage course, systematically. Direct coupling goes to the interference that this meeting brings about –5V voltage course to go up and noise on the –3.3V course of generation. In addition, stabilized voltage precision is quite poor also. Have ±10% only when precision of voltage of –5V power source when, this not accuracy also is met on the output tension that coupling produces to –3.3V.

 

Use below this kind of circumstance the I/O that the 2nd defect of linear manostat is linear manostat equipment cites a base (make can cite a base for example) will be reference with –5V. If need monitoring the electrify alignment of different voltage, need n transition possibly.

 

Graph 1. Produce negative tension linear manostat.
 

What the graph shows 2 times is same system, but used the linear manostat that presses a design for step-down negaive electricity only. These IC are called to lose linear manostat. The new-style ADP7183 of ADI company loses linear manostat to be restrained for lowermost noise, top power source only than (PSRR) and design. This makes the filter wave application that this parts of an apparatus suits sensitive to power source noise node very much.

 

Graph 2. Generation loses the negative linear manostat of voltage.

The negative linear manostat that if if pursue,use 2,shows, the –3.3V that arises is opposite undertake stabilized voltage at 0V ground voltage. This will produce low-down noise and accurate output tension. In addition, i/O cites a base with 0V it is reference systematically, can changeover of leave out n.

 

Come so, special negative linear manostat loses voltage in changeover or appear when filter wave negative voltage particularly important. The negative linear manostat on the market is supplied normally finite. The new product such as ADP7183(300 MA) and ADP7185 (500 MA) offerred more practicable range of products to design staff.