LINEAR Manuals

This application note presents the thermal model of LTM4600 DC/DC μModule regulator. The model includes thermal resistance from junction to top surface, from top surface to ambient, and the double-sided cooling scheme.

This document introduces Linear Technology's current sensing circuits

This Application Note describes a method to accurately measure internal and external phase and timing errors for a high performance direct I/Q modulator. A direct I/Q modulator, such as the LT5528, translates baseband I and Q signals to RF, and combines them to produce a modulated single sideband signal with (ideally) minimal residual carrier (LO feedthrough) and image signals (undesired sideband). In an ideal I/Q modulator, with perfect 90° phase shift between the I mixer and Q mixer local oscillators (LOI and LOQ), and with no other undesired phase and gain impairments, the modulator output will contain only the desired sideband. In practice, this is very difficult to accomplish. For example, with a requirement of –60dBc image suppression, the residual I-Q phase error is required to be below 0.16°. In practice, there are other sources of phase error, particularly in the baseband signal processing. Examples include baseband skew or other frequency dependent phase shifts in the modulator baseband circuitry; skew errors due to phase or delay mismatched baseband connection paths (e.g., cabling); and phase mismatch between the I and the Q paths in the baseband signal source (e.g., baseband DACs or signal generators.). These phase errors can cause RF output spectra to be shaped like those shown in Figures 1, 2 and 3.

This article discusses the application of linear regulators to post-regulate switching regulator outputs. Linear regulators offer benefits such as improved stability, accuracy, transient response, and lowered output impedance. However, they encounter difficulties in handling the ripple and spikes generated by switching regulators, particularly at higher frequencies. The article focuses on the impact of residual input-derived high-frequency components on the output of linear regulators.

ACPR (adjacent channel power ratio), AltCPR (alternate channel power ratio), and noise are important performance metrics for digital communication systems that use, for example, WCDMA (wideband code division multiple access) modulation. ACPR and AltCPR are both measures of spectral regrowth. The power in the WCDMA carrier is measured using a 5MHz measurement bandwidth. For ACPR, the total power in a 3.84MHz bandwidth centered at 5MHz (the carrier spacing) away from the center of the outermost carrier is measured and compared to the carrier power. The result is expressed in dBc. For AltCPR, the procedure is the same, except we center the measurement 10MHz away from the center of the outermost carrier. To measure ACPR and AltCPR, refer to the test setup shown in Figure 2. The DUT (device under test) is the LT5528, which is a high linearity direct I/Q modulator. It accepts WCDMA modulation at the baseband inputs, and generates a WCDMA modulated signal at the RF output. Note that a free running RF generator provides the LO signal. This type of generator is used because of its superior noise performance. This is critical, as a noisy LO signal may corrupt the modulator output, and consequently the ACPR measurement. For the generator shown, the automatic level control must be switched off to avoid degrading its broadband noise floor. Also,

This application note describes a method for accurately measuring the third order intercept point for low distortion IC products such as the LT5514. This includes the test setup, test equipment, test signal and interpretation of the measurement results.

delta sigma adc bridge measurement techniques

AN98-1 is a TI application note published in 2004. It introduces 18 circuit designs, including voltage controlled current source, signal source, conditioner and power circuit.

This document introduces the simple circuitry for cellular telephone/camera flash illumination, including LED and flashlamp two schemes, and detailed explanation of the flashlamp working principle and characteristics.

Slew rate verification for wideband amplifiers

This application note describes the use of the LTC1799 precision monolithic oscillator in various instrumentation applications, including transducer circuits, carrier-based amplifiers, sine wave generators, filters, interval generators, and data converters. The LTC1799 is a high-accuracy, high-stability RC oscillator that can be tuned over a wide range.

This article describes the bias voltage and current sense circuits for avalanche photodiodes (APDs) used in fiber optic systems. The APD module contains an APD and a trans-impedance amplifier, which converts the optical signal into an electrical signal. The APD requires a relatively high bias voltage to operate, typically ranging from 20V to 90V. Additionally, monitoring the APD's average current can indicate the optical signal strength and be used in conjunction with feedback techniques to maintain optimal signal levels.

This application note describes several low-cost coupling methods for RF power detectors that replace directional couplers. These methods allow for the integration of RF power detectors on-chip, which reduces cost and size. These methods also allow for the integration of RF power detectors and RF power amplifiers in a single module, which further reduces cost and size.

This is an article about current sources for fiber optic lasers.

This document describes a thermoelectric cooler temperature controller for fiber optic lasers, which can meet the requirements of precise temperature control to maintain stable performance of the laser.