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Method for a cross-quad peak amplitude detector

IP.com Disclosure Number: IPCOM000130562D
Publication Date: 2005-Oct-26
Document File: 7 page(s) / 431K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a cross quad peak amplitude detector. Benefits include improved functionality and improved performance.

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Method for a cross-quad peak amplitude detector

Disclosed is a method for a cross quad peak amplitude detector. Benefits include improved functionality and improved performance.

Background

              The amplitude of a signal can be measured using an amplitude detector. If results are required that are not sensitive to the signal’s rise and fall times (crest factor), a peak detector can be used. In that case, the result is a typical output DC voltage.

              The top-level design criteria for a peak detector are bandwidth, operating range, and linearity (see Figure 1). Figure 1A is a single ended type that is linear with a wide operating range but ripple is very high.

              Figure 1B is a differential type that has low ripple and medium operating range. The low end of the operating range is limited by high nonlinearity. The base emitter voltage (VBE) is constant for high signal levels, causing the other transistor to be completely turned off. However, the VBE drops when the signal level is low, causing the two transistors to split the current generated by  signal I30.

              Conventionally, the circuit in Figure 1B is widely used. To detect low signal levels, an amplifier may be required in front of the detector.

General description

              The disclosed method is a cross-quad peak amplitude detector. It combines two conventional configurations into a device with a wide operating range, including very low signal levels,

low ripple (differential), and high bandwidth-type of peak detector (see Figure 2).

              Figure 2A illustrates the circuit transition. Figure 2B illustrates the disclosed method.

Advantages

              The disclosed method provides advantages, including:

•             Improved functionality due to providing a solution for CMOS and other technologies in addition to bipolar devices

•             Improved performance due to providing high-speed operation, especially the unfolded version

•             Improved performance due to providing improved linearity

•             Improved performance due to eliminating the amplification in front of the peak detector for small input signals, especially the folded version

•             Improved performance due to providing low ripple

•             Improved performance due to providing differential operation

•             Improved performance due to providing a low value for the capacitor, especially for on chip designs

•             Improved performance due to being robust because the design is insensitive to temperature and process variations

Detailed description

              The disclosed method combines two conventional devices to create a cross-quad peak amplitude detector. The circuit illustrated in Figure 1A is included because of its capability to detect low-signal levels. Two of them are shown in Figure 2A in the form of I27, I29, X1 and X2. The input signal becomes differential. The switch, SW1, selects the node of the two with the highest voltage value. In Figure 2B, t...