15V-chopper-amplifier

Description: This circuit is a gain-of-1000 inverting amplifier designed to amplify submillivolt signals to levels suitable for further processing. In most system applications, utilizing maximum gain in the MAX420 is advantageous, as it minimizes the effects of offsets in later stages. For instance, if the circuitry following the MAX420 has an offset of 5 mV, the additional offset referred back to the MAX420 input (with a gain of 1000) will result in an offset of 5 µV, effectively doubling the system's offset error.

The described circuit employs the MAX420 operational amplifier configured as an inverting amplifier, which is characterized by its high gain and low noise performance. The gain of 1000 indicates that the input signal will be amplified 1000 times, making it suitable for processing very low-level signals. The inverting configuration is particularly useful in applications where signal inversion is not a concern, and it provides a straightforward method for achieving high gain.

The circuit typically consists of a feedback resistor (Rf) and an input resistor (Rin). The gain (Av) of the inverting amplifier can be calculated using the formula Av = -Rf/Rin. To achieve a gain of 1000, the values of Rf and Rin must be selected accordingly. For example, if Rin is set to 1 kΩ, Rf would need to be set to 1 MΩ to achieve the desired gain.

In practical applications, it is crucial to consider the bandwidth and slew rate of the MAX420, as these parameters will affect the amplifier's performance at high frequencies. Proper decoupling capacitors should also be used near the power supply pins of the MAX420 to minimize noise and ensure stable operation. Additionally, careful layout and grounding practices are essential to reduce parasitic capacitance and inductance, which can introduce unwanted noise and distort the amplified signal.

The circuit's design should also account for the input and output impedance, ensuring that the amplifier can interface effectively with subsequent stages of the signal processing chain. By maximizing the gain in the MAX420, the impact of any offsets introduced by following circuitry is significantly reduced, thereby enhancing overall system accuracy and reliability.This simple circuit is a gain-of-1000 inverting amplifier. It will amplify submillivolt signals up to signal levels suitable for further processing. In almost all system applications, it is best to use as OUTPUT much gain as possible in the MAX420, thus minimizing the effects of later-stage offsets. For example, if circuitry following the MAX420 has an offset of 5 m V, the additional offset referred back to the MAX420 input (gain = 1000) will be 5 p.V, doubling Fig. 3-4 the system"s offset error.